# Only getting 20MPG on 92 sentra....



## psalm143 (Aug 21, 2005)

Hello all I am having some problems with my 1992 Nissan Sentra 2-door automatic. It has 170,000 miles on it.

Ok so around a month ago I had 2 fuel injectors go out, so I replaced them with 2 used ones but they were in great running condition, and I put new O-rings on them when installed. I also decided to do a tune-up since it was past due, and this is all I did:

-New fuel filter
-new spark plugs (Bosch Platinum)
-New Spark Plug/Ignition wires (Duralast)
-New cap and rotor
-New PCV Valve
-Cleaned out Idle Air Control Valve
-New Air Filter
-New O2 Sensor
-Replaced old vacuum hoses

Alright so I filled her up with Chevron Gas, 89 octane I believe, and I ended up getting around 245 miles after filling up again with Chevron 89 around 8.6 gallons. So, thats around 28-29 MPG--GREAT! Well, today I had to put more gas in the car, and I ended up topping off with 9.975 gallons (I used Shell instead of Chevron), and that is on only 202 miles. Thats only 20.25 miles per gallon. I am stumped. BTW, this is all mostly city/some highway driving.

I pulled the spark plugs out today, and there is a slight amount of black carbon built up on the plugs, but only a very slight amount, not much at all. I am thinking maybe its running too rich for some reason? I looked at the tailpipe/exhaust and there is no carbon buildup or anything on the bumper. The car runs smooth, idles at around 7000 rpm, the exhaust doesn't really smell abnormal--I mean I don't smell anything rotten, maybe a slight pinch of a gas smell but I think thats normal. Also, I have noticed there is a slight amount of oil either being burnt or just escaping somewhere. After driving around 350 miles the dipstick went from the full mark to around 3/4 full. I can see a slight drip on the oil pan, maybe its the washer on the plug... But I dont see any puddles under the car ever, and I don't see any color of any smoke coming out of the tailpipe...

Does anyone have a guess or idea of the reason for this? The check engine light does not come on, it did before I replaced the O2 sensor but ever since then (a month) I haven't seen it come on even once. If anyone has any suggestions please let me know, I can provide any axtra info if it would help. Thanks for taking the time to read this, and let's hope I get more then 202 miles on this tank of gas...


----------



## B13boy (Dec 16, 2004)

Get those BOSCH plugs outta that Sentra!!!!!! Put factory, non-platinum NGK's
I get about 25-32mpg in mine... around 265miles a tank!


----------



## thestunts200sx (Jul 11, 2005)

i get around 300-375 miles to the tank on my 96 200sx se.

You've already changed a bunch of stuff.
Oil ??
Radiator flush ??

And yes, get NGK plugs, much much better then bosch.

Also, how do your tires look ? Believe it or not, having under or over flatted tires will affect your mpg.


----------



## psalm143 (Aug 21, 2005)

*hmm...*

Well, I have a set of non-platinum densos in my trunk, would those work better then the Bosch Platinums? I just can't believe that a spark plug like a Bosch Platinum could cause that poor of fuel economy. They claim to be the best and say they will get you the best fuel efficiency? And would they cause the MPG to drop that drastically, because that is 5-10 MPG? Thanks for the reply and lemme know if the denso are better for the car as I am broke and have to use what I have...

Also, tires are good, front is at 32psi, rear at 30psi. Trunk is almost empty, only a spare and a few tools, so no extra weight...


----------



## thestunts200sx (Jul 11, 2005)

NGK is the nest plug you can use for our cars.....
and thats all im gonna say.


----------



## B13boy (Dec 16, 2004)

Bosch makes great wiper refills and sparkplugs for vw's... get NGK, Nissan uses them for a reason! They are like $2 each at the dealer. Factory part# is 22401-50Y05, if you have to use aftermarket source get NGK's with the part number BKR5E-11 stamped on the plug.


----------



## B13boy (Dec 16, 2004)

My tech here at work said the the "head temp sensor" or the temp sensor for the ecu could be giving a false reading causing the ecu to think the engine is cold making it run rich, which in turn makes it the engine burn more fuel. Just a thought!


----------



## jp314 (Jun 18, 2002)

20mpg city on a GA16DE automatic only makes sense if you're always accelerating full throttle from stops.

b13boy mentioned the temp sensor. What does your temp gauge read? Does it reach normal operating temp? If the temp sensor is bad or has a bad connection, or the thermostat is stuck open, the ECU will stay in closed loop and run rich.

Your car only needs 87 octane - 89 is wasting money - UNLESS you have lots of deposits on the pistons, valves, etc. causing higher compression or hot spots, resulting in pre-ignition.

Bosch vs. NGK plugs will not cause a 10mpg difference, gotta be something else. NGK are better, last longer.

I'm sure new Duralast wires are O.K., but OEM plug wires are the best. I still have original wires (147,xxx miles) on my '93 se-r with bolt-on mods & S4 cams - runs great - 35.77 mpg over the last ~3000 miles, about 60%city/40%hwy.

You still might have a bad or leaking injector.

If you're using that much oil in 350 miles, you might want to determine the cause. You said there are no puddles, a compression & leak-down test might be in order.

Below is from my post on a different forum about bad mpg, listing more possibilities. That list is SE-R specific, some things will be different for a GA16DE automatic.
-----------------------------------------------------------------
Have you checked the oxygen sensor to see if it's working properly?

Put the ECU in diagnostic mode (see procedure below).
It would be easier using a Consult or Techtom MDM-100.
The check engine light on the dash will flash indicating a rich/lean
condition for the oxygen sensor. With the engine at normal operating
temperature, at about 2000 rpm, it should blink 5 times within 10
seconds. If it doesn't, you have a bad oxygen sensor, resulting in
bad mpg.

Another thing to check is your MAF ground wire.
How to re-ground your MAF:
http://www.se-r.net/engine/maf_ground.html


Look throught this a post I saved back in 2002, about bad mpg and things to try:
-----------------------------------------------------------------------------
On Thu, 31 Jan 2002 23:07:11 -0600 BlackSE-R <[email protected]> wrote:

>I think I'm beginning to lose my head. I have tried everything people have
>suggested to me. I checked the famous archives. I talked to mechanics. I
>keep on getting low miles per gallon. Last time I tanked: 137 miles; 8.402
>gallons. That's roughly about 16.3mpg. I drive a 92 se-r, no mods, 115k
>miles on it, I bought it from this one guy who had to sell it, because he
>was forced to leave the country. Other se-rs get more than 20mpg. Guys, if
>this happens to me, I'm popping the Champaign bottles and having a huge
>party. Any suggestions on how I can fix this problem? I'm hopeless now...
>Thank you up front, for any suggestions...

Yep, your mileage sucks. Something is wrong. It's not hopeless. Don't
lose your head, use your head. You can fix this.
For good mpg, your car needs sufficient well-mixed, accurately metered
air/fuel, good compression and a properly-timed good spark in all 4
cylinders, efficient transfer of power to the wheels, and an minimally
restrictive exhaust system. That's all.
-ECU show any codes? If your ECU never gets out of open-loop mode (or is
stuck in fail-safe) you will waste a LOT of fuel...16mpg sounds about
right. All critical sensors (O2, TPS, crank angle, MAF, coolant temp,
knock sens.) must operate in approved range to reach closed-loop (feedback).
-Spark plugs show any clues? Lean, rich, oil? Are they the right plugs,
properly gapped? Don't mess with anything but spec NGK plats...you can use
5's if 6's foul.
Have you:
-checked the O2 sensor function via the ECU diagnostic?
-verified idle speed 850/ignition timing at 15-17 deg. BTDC (and not, say,
10 deg)?
-regrounded the MAF and checked for proper function?
-looked for vacuum or intake air leak(s)? (idle manifold pressure should be
steady 18-19 inHg @sea-level) Check the AAC/FICD, (cold-)air regulator,
EGR, PAIR, and PCV valves for proper function.
-thoroughly cleaned the TB/intake manifold? Lots of gunk builds up here.
-replaced/cleaned the air filter?
-checked battery, alternator, coil, corroded connections etc. as potential
cause of weak spark under load?
-checked clutch for gross slippage (you'd probably have noticed
this...popping clutch in 5th @idle should stall engine)
-checked wheels for proper tire pressure and alignment?
-checked brakes (incl parking brake) to be sure they aren't dragging?
-checked fuel system for leaks, proper fuel pressure, dirty filters? (there
was a recall on pre-93(?) fuel pumps...check w/ dealer to see if yours was
done.)
-checked your cat. converter and muffler for fouling/blockage?
-looked for a dead cylinder? Check for healthy spark and compression
(misfire: fouled plug, bad HT wires, bad distributor cap/rotor; OR fuel:
dirty/plugged fuel injector; OR mechanical: worn/bad piston
rings/valves)? A dead cylinder would waste about 25% of your fuel, so
again 16mpg sounds about right.

Good luck!
-----------------------------------------------------------------------------


ECU diagnostic mode:
----------------------------------------------------------------------
Self-diagnostic system will operate in 2 modes which are
manually selected using a screwdriver through access port on ECM. With
ignition switch in ON position and engine not running, use screwdriver
to turn switch fully clockwise. Wait at least 2 seconds. Turn
screwdriver fully counterclockwise. Inspection light will begin to
flash.

NOTE: Modes cannot be switched while engine is running. When
ignition switch is turned to OFF position while in Mode II,
ECM switches to Mode I.

Mode I (Bulb Check)
Engine is not running in this mode. Turn ignition switch to
ON position. Red LED on ECM and CHECK ENGINE light (if equipped)
should be lit. If lights do not illuminate, check and replace bulbs as
necessary.

Mode I (Malfunction Warning)
This is normal vehicle operating mode and engine must be
running. On California vehicles, if a malfunction occurs, Red LED and
CHECK ENGINE light (if equipped) will illuminate, indicating an engine
control system malfunction has occurred and a code has been stored. On
Federal vehicles, codes are stored and only Red LED will illuminate
when ECM’s Central Processing Unit (CPU) malfunctions.

Mode II (Self-Diagnostics)
When Mode II is accessed (engine not running), codes stored
in ECM memory will be flashed by CHECK ENGINE light (if equipped) and
Red LED on side of ECM.
Long flashes (.6 second) indicate first digit of code. Short
flashes (.3 second) indicates second digit of code. For example: one
long flash followed by 2 short flashes indicate a Code 12.

DTC 33, OXYGEN SENSOR
1) Check System Function
During self-diagnostic test Mode II, Red LED on ECM and MIL
on instrument panel should blink 5 times within 10 seconds when engine
speed is about 2000 RPM.
----------------------------------------------------------------------


----------



## psalm143 (Aug 21, 2005)

Well I checked the ECU and it shows no codes, or code "55" which means everything is operating ok. If an injector was leaking, wouldnt it throw a code? Also, the temp guage works fine, when I start the car it is on cold, and after driving it for approx 2-3 minutes it gradually rises to the mid-range.

Honestly, I still cant figure this out. Even before I had the injector problems, with a bad O2 sensor I was still getting 22-25 MPG. Unless I plugged a vacuum hose line or something in the wrong place, I cant figure it out. The car idles very smooth, no roughness at all, so it is hitting on all four, it accelerates very smoothly, I cant really notice any lack of power (although the car itself lacks power as it is a 1.6), so I think that rules out vacuum problems...

As I said before, the spark plugs show a light build-up of black carbon, but not a great deal of it. They were factory gapped at .44. I dunno, maybe I am just crazy, I am going to see about re-grounding the MAF, and check all of the sensors out again. But still, if one wasn't functioning wouldn't it throw a code?

I just filled the tank up with gas, and I have gone 30 miles, and now the guage is at the 3/4 mark, I feel like every time I have to stop I can see the guage going downhill, it really sucks! I looked at the injectors, don't see any gas leaking from the top, so seals arent broke, and I dont think I can smell any gas sooo, who knows....


----------



## psalm143 (Aug 21, 2005)

Also, just wanted to say that I sprayed carb cleaner on all of my vacuum lines, and I didnt notice any difference in the engine while doing so, so no leaks. I also have checked over the exhaust, and it is not blocked up or anything...

To be quite honest, the car runs incredibly, it idles smoother then ever, it sounds extremely healthy, it is just guzzling gas somehow. Is there a way to adjust the air/fuel ratio somehow? If so, maybe the ratio was thrown off by something.

Also, to clarify the oil leak, it has only lost .5 quartz instead of what i said before, as it is still in the halfway mark of the dipstick, so I think a new washer on the plug will fix that.


----------



## pimpride (Mar 28, 2005)

Are your tires at the right psi like mentioned before? Check on your door jamb to see the correct pressure (What's on the tire isn't always right).


----------



## psalm143 (Aug 21, 2005)

pimpride said:


> Are your tires at the right psi like mentioned before? Check on your door jamb to see the correct pressure (What's on the tire isn't always right).


Yeah as already stated they are at the recomended setting. 32psi front, and 30psi rear (actually 29 is recommended for rear).


----------



## thestunts200sx (Jul 11, 2005)

psalm143 said:


> Yeah as already stated they are at the recomended setting. 32psi front, and 30psi rear (actually 29 is recommended for rear).


your running stock wheels and tires, right ?

Cause if not, maybe your speedo isnt calibrated correctly.

Maybe you should get your cluster checked to make sure its reading correctly.


----------



## Kindfiend (Oct 13, 2004)

psalm143 said:


> Also, just wanted to say that I sprayed carb cleaner on all of my vacuum lines, and I didnt notice any difference in the engine while doing so, so no leaks. I also have checked over the exhaust, and it is not blocked up or anything...
> 
> To be quite honest, the car runs incredibly, it idles smoother then ever, it sounds extremely healthy, it is just guzzling gas somehow. Is there a way to adjust the air/fuel ratio somehow? If so, maybe the ratio was thrown off by something.
> 
> Also, to clarify the oil leak, it has only lost .5 quartz instead of what i said before, as it is still in the halfway mark of the dipstick, so I think a new washer on the plug will fix that.


Still haven't ruled out the coolant temp sensor, right? It's not the sensor for the gauge, so that won't tell you anything. I would take a look at it, check the resistance when cold (room temp) to hot (run it under hot water for a bit). The resistance should go down as it gets warmer. Haynes says 3000 oms @ 60 degrees F and 300 oms @ 180 degrees. 

Good luck, I feel for you with these gas prices.


----------



## mille-16i (Jun 16, 2004)

I would say replace your CTS as stated before that is the #1 cause of running rich and the last thing replaced go figure. Also put a Thermostat in and purge the cooling system. You have two to three temp sensors on your car one for the dash(Sender) one for the ECU(Sensor) and sometimes one for the fans so get the right one it is a Temp Sensor.


----------



## psalm143 (Aug 21, 2005)

thestunts200sx said:


> your running stock wheels and tires, right ?
> 
> Cause if not, maybe your speedo isnt calibrated correctly.
> 
> Maybe you should get your cluster checked to make sure its reading correctly.


No man im rollin on 20's (Just kidding). Yes they are stock...

Well I guess I will check the resistance of the CTS tomorrow morning. I would do it now but I think it is still raining out soo... Hopefully, if it is not operating right I can fix/replace it and my problems will be solved.


----------



## mille-16i (Jun 16, 2004)

psalm143 said:


> No man im rollin on 20's (Just kidding). Yes they are stock...
> 
> Well I guess I will check the resistance of the CTS tomorrow morning. I would do it now but I think it is still raining out soo... Hopefully, if it is not operating right I can fix/replace it and my problems will be solved.


Really it is only like a 30 dollar part and should e included in a good tune up I would just replace it myself


----------



## psalm143 (Aug 21, 2005)

jp314 said:


> -ECU show any codes? If your ECU never gets out of open-loop mode (or is
> stuck in fail-safe) you will waste a LOT of fuel...16mpg sounds about
> right. All critical sensors (O2, TPS, crank angle, MAF, coolant temp,
> knock sens.) must operate in approved range to reach closed-loop (feedback).


I have a question regarding the open-loop or fail-safe mode. How exactly can I detect this? Do I have to individually check each sensor or would the ECU tell me it was stuck in this mode? Any help is greatly appreciated, and I thank all for your replies...


----------



## bob89sentra (Sep 15, 2005)

Was it just one tank of gas? I have gone to gas stations and put 7 gallons in a standard 5 gallon gas can  The pump could be out of calibration.
I wouldn't start paniking after just one fillup. If the mileage stays constant for more than 2 tanks then I would check into things like the coolant sensor.


----------



## psalm143 (Aug 21, 2005)

bob89sentra said:


> Was it just one tank of gas? I have gone to gas stations and put 7 gallons in a standard 5 gallon gas can  The pump could be out of calibration.
> I wouldn't start paniking after just one fillup. If the mileage stays constant for more than 2 tanks then I would check into things like the coolant sensor.


Well, I guess there could be logic to that, but I highly doubt that it's the case. I put 10 gallons and topped off my tank, and my fuel guage went up past the "Full" mark. I also noticed the same symptoms the tank before. I can tell it is still not getting anywhere close to good gas mileage, as I have driven 45 miles on this tank and the guage is now at 2/3.

The question I have is if the CTS, or engine temp sensor was bad, would it cause a drastic gas mileage decrease? I mean I am maybe only getting 15-20 mpg now. Also, on top of that, would it affect the way the engine/exhaust sounds, or even the driveability? Would it cause a check engine light to come on? I ask these questions because as I said before, my car is running great, it idles fine, accelerates fine, everything seems normal, no ECU codes. However, the gas mileage is the only symptom of whatever is wrong... So I am just asking everyone that might have more experience then me on Sentra's what they think could cause the milage decrease, with virtually no symptoms?


----------



## B13boy (Dec 16, 2004)

The temp sender for the ecu is different then the one for the gauge. My fuel gauge is all wack too! I go about 35miles and 1/4 tank of fuel is gone, then about 110miles it's at 1/2, but it still goes 300miles per tank. The gauge looks like -1/8 tank of fuel but it will go 300, it used to freak me out how fast the gauge drops, but you have to run the tank almost empty a few times to get the true mpg. I also notice that i get better gas mileage out of cheap gas then premium.


----------



## Kindfiend (Oct 13, 2004)

psalm143 said:


> Well, I guess there could be logic to that, but I highly doubt that it's the case. I put 10 gallons and topped off my tank, and my fuel guage went up past the "Full" mark. I also noticed the same symptoms the tank before. I can tell it is still not getting anywhere close to good gas mileage, as I have driven 45 miles on this tank and the guage is now at 2/3.
> 
> The question I have is if the CTS, or engine temp sensor was bad, would it cause a drastic gas mileage decrease? I mean I am maybe only getting 15-20 mpg now. Also, on top of that, would it affect the way the engine/exhaust sounds, or even the driveability? Would it cause a check engine light to come on? I ask these questions because as I said before, my car is running great, it idles fine, accelerates fine, everything seems normal, no ECU codes. However, the gas mileage is the only symptom of whatever is wrong... So I am just asking everyone that might have more experience then me on Sentra's what they think could cause the milage decrease, with virtually no symptoms?


I believe that if the coolant temp sensor is bad, your ECU will never get out of open loop. That would cause your milage to suck as much as you say it does. Driveablility might not be affected too much, like the car never warmed up. I could be wrong about that, however, and I would think a bad CTS would throw a code.


----------



## psalm143 (Aug 21, 2005)

Kindfiend said:


> I believe that if the coolant temp sensor is bad, your ECU will never get out of open loop. That would cause your milage to suck as much as you say it does. Driveablility might not be affected too much, like the car never warmed up. I could be wrong about that, however, and I would think a bad CTS would throw a code.


Alright well thanks for all of the replies, I looked at what I think is the Coolant temperature sensor (to the left of fuel injectors, on passengers side, just a little bit lower then the injectors, and it is just above a coolant line that runs maybe 6-8 inches downward, it has a wire harness plugging into it), and I unplugged the sensor and tried to get a reading for the OHMs with ignition turned to "on", but no luck with my digital voltmeter. However, there is also another sensor type thing just below the sensor I just described, only this one has a wire harnes that looks as if it is permanently attatched to what looks like an extremely long bolt that is screwed into something (sorry, its hard to describe).

So, I think I will just run this tank to empty and see how many miles I can get, and on the 10th I will buy a new CTS and install it (the 10th is payday). I will keep you all updated when I figure this all out! Thanks Again!


----------



## B13boy (Dec 16, 2004)

The CTS is by the tstat housing near the intake manifold, it has a two prong connector that looks like a fuel injector connector. Should cost about $25. You can get it from nissanparts2u.com for $19.92 part number 22630-51E02


----------



## pimpride (Mar 28, 2005)

psalm143 said:


> Yeah as already stated they are at the recomended setting. 32psi front, and 30psi rear (actually 29 is recommended for rear).


Then you should be running 29 in the back. Overinflation can cause bad gas mileage just as easily as under inflation. Not to mention uneven treadware.


----------



## psalm143 (Aug 21, 2005)

pimpride said:


> Then you should be running 29 in the back. Overinflation can cause bad gas mileage just as easily as under inflation. Not to mention uneven treadware.


Well, yeah I know that. But it has been a mix of rain/sunshine in the past week where I live and the psi seems to always change... I will re-check them today, and thanks for letting me know where the CTS is..


----------



## psalm143 (Aug 21, 2005)

B13boy said:


> The CTS is by the tstat housing near the intake manifold, it has a two prong connector that looks like a fuel injector connector. Should cost about $25. You can get it from nissanparts2u.com for $19.92 part number 22630-51E02


Well is it pretty much underneath the IACV, and beside the first injector from the passenger side?

I looked in a sentra manual, but it was for 95 and newer models, and it shows it underneath the distrubutor, but I cannot find any 2-prong connector that looks like a CTS underneath the distributor.


----------



## pimpride (Mar 28, 2005)

It is down and behind the IACV. It has a plug sticking off the top of it. I think the plug is red, but that may be irrelevant.


----------



## 240on430 (May 3, 2005)

How can overinflation create low mpg?


----------



## psalm143 (Aug 21, 2005)

240on430 said:


> How can overinflation create low mpg?


I am not really sure, but my only guess is that if you have certain tires overinflated, then it can make the cars driveability unbalanced. But I don't really think it makes much difference as of whether you have 29 psi or 30 psi, just as long as it is the same on both sides of the car, and as long as it is only + or - 1 or 2 psi.

On a side note I just started working at a rental car/car sales place, and my job is to wash/detail rental cars, along with check fluids &/or tire pressure. When I started last weekend every single car I washed had underinflated tires at least by 4-6 psi (according to what the car recommended on the sticker inside the drivers door), so go figure... I had to re-inflate each one, which made my job a hell of a lot harder, especially when I am suppose to be doing each car in 20 minutes...


----------



## pimpride (Mar 28, 2005)

240on430 said:


> How can overinflation create low mpg?


It will cause your tires not to sit flat on the pavement.










You wont get as good of traction.


----------



## psalm143 (Aug 21, 2005)

I was just wondering if anyone knew for sure whether a bad Coolant Temperature Sensor would throw a code on a 92 sentra. I looked at all of the possible codes for 91-94 models at http://www.sentra.net/tech/ecu.php?, and it does not show any code for a CTS (although the 95-current ones do)... So does that mean that if mine is not operating correctly that the ecu wont tell me anything about the problem? The reason I ask is I cannot figure out how to test the Ohms on it so, I am just trying to determine if it is really the cause?


----------



## Catman (May 21, 2004)

psalm143 said:


> I was just wondering if anyone knew for sure whether a bad Coolant Temperature Sensor would throw a code on a 92 sentra. I looked at all of the possible codes for 91-94 models at http://www.sentra.net/tech/ecu.php?, and it does not show any code for a CTS (although the 95-current ones do)... So does that mean that if mine is not operating correctly that the ecu wont tell me anything about the problem? The reason I ask is I cannot figure out how to test the Ohms on it so, I am just trying to determine if it is really the cause?


psalm143, the code would be 13, at least thats what my Haynes manual says. It says a failure in the coolant temperature sensor circuit should set a Code 13. I removed my CTS, and it tested good. It has a metal tip, so I suspect problems may happen more with corrosion of the wiring harness. Regarding your problem, I would replace the Bosch plugs. The regular ones I used for 1,000 miles were carbon fouled. Put NGK plugs back in and have had no problems with fouling since. I have no name plug wires my mechanic put on last fall, and I just passed emissions with no problems. In my experience, the NGK plugs are the key. I also am using an OEM PCV valve. Getting close to 35 on the highway, and 27 in city/mixed driving. I also use a product called Fuel Power 60 every fill-up. I lost one injector two times, but no injector problems since I started using FP60 last fall. Actually, my car runs better than it has for years. It seems injector problems happen on these cars, so maybe a safe injector cleaner may help, especially after running those Bosch plugs. In my case, I failed emissions right after using those Bosch plugs. Just my experience. Hope it helps. Another thought, I do notice a decrease in mileage as outdoor temps drop. Winter mileage is in the lower twenties, which seems to be related to the engine being cold. Is it getting colder in your area?


----------



## psalm143 (Aug 21, 2005)

Catman said:


> psalm143, the code would be 13, at least thats what my Haynes manual says. It says a failure in the coolant temperature sensor circuit should set a Code 13. I removed my CTS, and it tested good. It has a metal tip, so I suspect problems may happen more with corrosion of the wiring harness. Regarding your problem, I would replace the Bosch plugs. The regular ones I used for 1,000 miles were carbon fouled. Put NGK plugs back in and have had no problems with fouling since. I have no name plug wires my mechanic put on last fall, and I just passed emissions with no problems. In my experience, the NGK plugs are the key. I also am using an OEM PCV valve. Getting close to 35 on the highway, and 27 in city/mixed driving. I also use a product called Fuel Power 60 every fill-up. I lost one injector two times, but no injector problems since I started using FP60 last fall. Actually, my car runs better than it has for years. It seems injector problems happen on these cars, so maybe a safe injector cleaner may help, especially after running those Bosch plugs. In my case, I failed emissions right after using those Bosch plugs. Just my experience. Hope it helps. Another thought, I do notice a decrease in mileage as outdoor temps drop. Winter mileage is in the lower twenties, which seems to be related to the engine being cold. Is it getting colder in your area?



I live in southern california, the desert area so no the temperatures have not decreased (85-90 degrees daily).

I pulled the Bosch spark plugs out today, and each one is black carbon covered on the very bottom thread. I put Denso standards in because I already have them, I know they wont fix my problem and yes I will put NGK's in as soon as I have some money to do it. I still am clueless though, as when I did the tune-up, after the first fill-up, I got decent gas mileage, and then after driving 300 miles or so the mileage just got really bad, and it has been since. My hope is that the Bosch plugs turned to crap after the 300 miles, and they weren't operating right since, but that is really a long shot.

I also am hoping an oil change and radiator flush might fix the rich running condition, because I remember while I was doing the tune-up I accidentally pulled a coolant hose (the one near the CTS), and a bunch of coolant came flying out, so I added water to the coolant to bring it back to full (so maybe that caused some air pockets or the mixture is now far off or something). And even though I changed the oil 2500 miles ago my car also ran dead with a list of problems from those 2 bad injectors so maybe some crap got into the oil.

Well I wont rule out the coolant temp sensor, I just cant believe that it would go bad and no check engine light would come on indicating it, but who knows I guess...

Also, the PCV valve I have in my car is brand new, not sure if it is OEM though, I got it from Autozone so it probably isnt. I didnt think it would really matter (same thing for the fuel filter I got).


----------



## lfd75 (Nov 27, 2004)

This might be a long shot but did you check your timing after changing the cap and rotor? If it´s too retarded you might run rich.


----------



## psalm143 (Aug 21, 2005)

lfd75 said:


> This might be a long shot but did you check your timing after changing the cap and rotor? If it´s too retarded you might run rich.


I don't think its a long shot at all, I just dont have a timing gun and as I said before I am broke and will be for a few weeks so I cant take it to a shop for them to check it out...

I am not too familiar as far as the timing goes, I have never messed with it before so...

Im just in the middle of switching jobs (I quit one), and now I have two new ones so it is just a matter of waiting until I get my first checks.... Thanks for the suggestion.


----------



## whatS3R (Jul 28, 2005)

hey question ... my timing is off and i havent had the chance to get a haynes manual ... how do you check the timing on the car ... im used to push rod pontiac 2.8's haha (rebuilt 86 Pontiac Fiero) and its gotta be different and in a dif spot so ??


----------



## Catman (May 21, 2004)

whatS3R said:


> hey question ... my timing is off and i havent had the chance to get a haynes manual ... how do you check the timing on the car ... im used to push rod pontiac 2.8's haha (rebuilt 86 Pontiac Fiero) and its gotta be different and in a dif spot so ??


This may give you some ideas: http://www.g20.net/forum/showthread.php?s=&threadid=13470

I have not needed to adjust my timing, but the above article may help in understanding the timing marks on the flywheel and procedure on Nissan's.


----------



## psalm143 (Aug 21, 2005)

Catman said:


> Regarding your problem, I would replace the Bosch plugs. The regular ones I used for 1,000 miles were carbon fouled. Put NGK plugs back in and have had no problems with fouling since. I have no name plug wires my mechanic put on last fall, and I just passed emissions with no problems. In my experience, the NGK plugs are the key.


Alright well since I have no codes for the Coolant Temp Sensor, then I am not going to replace it yet. I bought a set of NGK plugs today (BKR5E-11) from Kragen Auto, and I will install them in the morning. Also I bought some Chevron Supreme Oil 10w-30 and a Bosch filter to do an oil change as well (its only been 2500 miles but after going through all the crap I did with the injectors, plugs, smoke, etc) I think it should defenitely be changed. I will also fill up at Chevron and I will let everyone know how it goes when I figure out the mileage on the next fill-up.

BTW, I thought of something I did/didn't do that could be causing a problem... I never pre-gapped thos Bosch plugs, I just figured the box said .44 so it was already good. So I bought a Gapper for the NGK's and I gapped them all to .44 a minute ago so well see what happens.

If the NGK plugs and the oil doesnt fix or improve the problem, then I will flush /purge the coolant system and replace the Coolant temp sensor. Thanks for all of the help and I will keep everyone updated...


----------



## psalm143 (Aug 21, 2005)

Well, I was so excited to get the plugs in and oil changed, that I did it tonight. I drove it for 30 miles on highway driving and I can honestly say that this car roars like a beast! It drives a lot smoother, and once you hit 3rd gear or so it will really hit speeds (it is an auto though). I filled the tank up with the cheapest Chevron too, so lets just hope I can get 250-300 miles on this tank. I think the NGK plugs really did make a difference, hard to tell though until driven for a few days. I really wish I had some more money so I could drive to los angeles or somewhere near there just because I am excited to drive the car since its running great, but you know how gas is these days... Maybe next week.


----------



## Catman (May 21, 2004)

When my mechanic put the Bosch plugs in, my car seemed sluggish. NGK's brought back the peppy engine I was used to. Hope this resolves your mileage issue.


----------



## mille-16i (Jun 16, 2004)

A CTS will only send a code if it is a hard fail ie no signal at all cause the B13 is not a smart ECU and cannot tell if the engine is really 10 degrees or if the CTS is off its rocker. To test the CTS hook up an ohm meter to the prongs on the sensor itself you will need the proper specs for the CTS as to Temp when my CTS failed my ECU said no problems and I run non NGK plugs and get 30+ mpg with a heavy ass left foot.


----------



## mille-16i (Jun 16, 2004)

pimpride said:


> It will cause your tires not to sit flat on the pavement.
> 
> 
> 
> ...


You will accually get a wee bit better milage if they are over inflated but you will have worse traction cause your footprint will be smaller but up to 35psi on normal tires will not effect any thing as long as you are not exceeding the max presure on the tire itself.


----------



## psalm143 (Aug 21, 2005)

mille-16i said:


> A CTS will only send a code if it is a hard fail ie no signal at all cause the B13 is not a smart ECU and cannot tell if the engine is really 10 degrees or if the CTS is off its rocker. To test the CTS hook up an ohm meter to the prongs on the sensor itself you will need the proper specs for the CTS as to Temp when my CTS failed my ECU said no problems and I run non NGK plugs and get 30+ mpg with a heavy ass left foot.


Will a digital Multimeter work? If so, what setting do I put it on? Also, do I check the ohms with the car turned on as well, even if the CTS is not plugged in?


----------



## Catman (May 21, 2004)

I used a digital ohm meter. Removed the CTS and used this write-up from Alldata as a guide: 

Immerse sensor in water at specified temperatures and check resistance with an ohm meter.
Resitance should decrease as temperature increases.

TEMPERATURE: 68°F (20°C)
Resistance: 2.3 - 2.7 K ohms
TEMPERATURE: 94°F (90°C)
Resistance: .24 - 0.26 K ohms
TEMPERATURE: 230°F (110°C)
Resistance: 0.14 - 0.15 K ohms

Replace the sensor if it fails the above test.

I only put it next to a thermometer at 68 degrees. It was in spec, so I figured it was OK, and my current performance confirms it. Also, resistence was lower when installed in a warm engine, so it seemed to be decreasing in resistance when warm.


----------



## psalm143 (Aug 21, 2005)

Catman said:


> I used a digital ohm meter. Removed the CTS and used this write-up from Alldata as a guide:
> 
> Immerse sensor in water at specified temperatures and check resistance with an ohm meter.
> Resitance should decrease as temperature increases.
> ...


Alright well I will try to get a reading with it in the engine... If I had another CTS it would make sense because I could install it and not loose so much coolant, but If I just un-bolt it and pull it out Im sure coolant will come pouring out... Now I am having a problem with my trip meter, it is stuck on 6.9. If I juggle the clear push button it starts to move but it will get stuck again, the actual cars mileage meter doesnt stick though, weird ehh? And that makes it a little harder for me to tell what kinda mileage it is getting now, go figure!


----------



## Catman (May 21, 2004)

When I pulled the CTS I only lost maybe a few drops, but the engine was only a little warm, not hot. The CTS is next to the air bleed bolt. You might get some air coming out if you have an air pocket, but if the car is level and fairly cool, then coolant loss should be minimal. I removed it just because I did not know how warm it was in the car. I did take readings as the car cooled off and before removing, so I could see resistance changing. So, I suppose you could get a ballpark reading by testing it in the car, estimating coolant temperature somehow. My only problem is that I broke part of the harness unclipping it. Be careful when doing that.

I usually record mileage on my gas receipts, then subtract mileage from the previous receipt to get miles traveled. It may take a little more time, but will get accurate milage traveled.


----------



## psalm143 (Aug 21, 2005)

*update...*

I just thought I would let everyone know that my car has been getting better mileage. I never tested or checked the Coolant Temperature Sensor either. I just filled up again and my car went 257.5 miles on 9.5 gallons of 87 octane fuel, and that was like 70% city 30% highway. Thats around 27 MPG which aint bad. The car was originally rated 27 city and 33 highway.

I think one of my main problems is that my tripometer doesnt match up to my mileage on the odometer. My trip meter said only 215 miles on this last fillup, but when I subtracted the actual miles (167514, to 167771.5), they dont add up, because that is 257.5. It gets stuck sometimes so that was probably one of my main problems in the first place as that was what I went off of for the miles I traveled.

Anyways, thanks again for all of the help...


----------



## rx7racr (Jan 25, 2004)

I'm having your EXACT problem, and I'm afraid I'm gonna go broke chasing it!

(the car won't pass emissions as a result, so I keep paying for emissions tests after every attempted fix!)

any updates for us? did your mileage stay up?


----------



## psalm143 (Aug 21, 2005)

rx7racr said:


> I'm having your EXACT problem, and I'm afraid I'm gonna go broke chasing it!
> 
> (the car won't pass emissions as a result, so I keep paying for emissions tests after every attempted fix!)
> 
> any updates for us? did your mileage stay up?


Yes, my mileage has stayed up. I have been averaging around 26 miles per gallon and that is mostly city driving. Once a week I drive a 200 mile round trip on a strictly highway basis, and when I fill up after doing that the mileage is usually around 29-30 mpg.

I mean its not a perfect running car, it has nearly 173000 miles on it, but considering all of the above I cant really complain because it is still running pretty decent. I haveent had to smog it since I have had the car, so I am lucky in that regard (I am not really sure if it would pass).

When you got your car smogged, did it pull up any ECU errors, or did they say what the likely factor was in your car not passing? Good luck in figuring it all out, and let me know if I can be of any help...


----------



## rx7racr (Jan 25, 2004)

thanks for the response.. 

my 1992 car only has *77,000* miles on it!!! I bought it because I thought "hey - that's practically brand new for a sentra!". At the time, I actually had a 1991 with 154,000 on it which I sold to, as i thought - "upgrade."

The ECU isn't throwing ANY codes, and there's no check engine light. I've replaced the thermostat, spark plugs (NGK), O2 sensor, and fixed air-leaks, ECT sensor corrosion, and I've checked resistances all over (making sure everything is well connected to "ground". My tires are perfectly inflated, but the car will not get over 23mpg. 


I need to re-state that the car runs PERFECTLY. I'm really starting to get frustrated with this, because in CT, they charge you every month that you haven't passed emissions - - I'm actually getting a monthly bill from the government because this ggddddmn car won't pass (it's blowing high CO's indicating rich running)!


----------



## oliverr87 (Sep 23, 2005)

Catman said:


> . It seems injector problems happen on these cars, so maybe a safe injector cleaner may help,


Injector problems do NOT happen on these cars. They only happen because people are always using those injector cleaners. I have only used one bottle ONCE in the cars 12 year lifespan and that was because the car was sitting for 2.5 years, and I did not know the condition of the fuel lines, etc. I just used it for preventive measures. Use ONLY Redline, Chevron Techron, or 3M from the Nissan dealer. The injectors are SELF-CLEANING and do NOT need injector cleaners because modern injector cleaners contain additives that EAT away the injectors. Redline, Chevron Techron, and 3M are the ONLY certifiable cleaners. You could be shortening the life of your injectors.


----------



## psalm143 (Aug 21, 2005)

rx7racr said:


> thanks for the response..
> 
> my 1992 car only has *77,000* miles on it!!! I bought it because I thought "hey - that's practically brand new for a sentra!". At the time, I actually had a 1991 with 154,000 on it which I sold to, as i thought - "upgrade."
> 
> ...


Well I wish I could help you fix the problem, but I am no mechanic. All I know is that I just replaced everything, a full tune-up, and somehow it fixed the problem. As I stated earlier in the thread, I did everything that you mentioned, but I also changed the fuel filter, Ignition wires, Cap and Rotor, PCV Valve, cleaned IACV, cleaned throttle body, Air Filter, & 2 used injectors as they took a crap somehow.

One thing people always suggested to me was to check the resistance of the CTS (Coolant Temperature Sensor), because they said if it isnt functioning properly than it could easily cause the mpg decrease (& rich running condition), and it wouldnt throw a code. Just search for CTS or Coolant Temp Sensor on the forums and it will come up with a bunch of threads on how to check it/what resistance is normal (And its a cheap part to replace).

Good luck and let me know how it goes....


----------



## psalm143 (Aug 21, 2005)

oliverr87 said:


> Injector problems do NOT happen on these cars. They only happen because people are always using those injector cleaners. I have only used one bottle ONCE in the cars 12 year lifespan and that was because the car was sitting for 2.5 years, and I did not know the condition of the fuel lines, etc. I just used it for preventive measures. Use ONLY Redline, Chevron Techron, or 3M from the Nissan dealer. The injectors are SELF-CLEANING and do NOT need injector cleaners because modern injector cleaners contain additives that EAT away the injectors. Redline, Chevron Techron, and 3M are the ONLY certifiable cleaners. You could be shortening the life of your injectors.



I disagree, at least in my case. I had to replace two injectors on my 1992 sentra, and I had never used any fuel injector cleaner at all. And I inherited this car from my brother, and he had the car since it was new, and he never used any injector cleaner either.

However, I did use a bottle after the first two went, and ended up replacing two more. The two I most recently replaced were the other two "original" ones. So, in my case the injector cleaner has not caused my injector problems...

That is not, however, to say that I wont have any further injector problems, but I do hope that I don't!


----------



## oliverr87 (Sep 23, 2005)

psalm143 said:


> I disagree, at least in my case. I had to replace two injectors on my 1992 sentra, and I had never used any fuel injector cleaner at all. And I inherited this car from my brother, and he had the car since it was new, and he never used any injector cleaner either.
> 
> However, I did use a bottle after the first two went, and ended up replacing two more. The two I most recently replaced were the other two "original" ones. So, in my case the injector cleaner has not caused my injector problems...
> 
> That is not, however, to say that I wont have any further injector problems, but I do hope that I don't!


Ok, then I should say it is RARE and that it DOES happen. But NOWHERE has anybody claimed definitively that the B13 injectors are faulty at any level.

BTW psalm143, where are you located?


----------



## psalm143 (Aug 21, 2005)

oliverr87 said:


> Ok, then I should say it is RARE and that it DOES happen. But NOWHERE has anybody claimed definitively that the B13 injectors are faulty at any level.
> 
> BTW psalm143, where are you located?


Im in Southern California, in the Lancaster/Palmdale area....


----------



## insp09 (Jan 26, 2006)

I'm just not sure I have the right thermostat in my B13. Where should the needle on the temp gage be, normally? A little lower than the middle?


----------



## MisterRx (Feb 8, 2006)

I also have 92 Sentra E. Currently getting 21-23mpg. on city roads. I can drive 270 km (city ,rural Canada) before my next fill up. (about 1/4 of tank remain fillled). On hwy I get 400 km looks ok anything wrong.

I changed cap, rotor, spark plug, pcv valve, oxygen sensor. New Radiator, new exhaust system, ball joints, starter, battery.

Sometime I get gas fume smell in winter when start the car. After awhile the smell disappear. Is it Charcoal Canister-cracke hose? In summer I rarely get gas smell. I was thinking in winter fuel injector using more fuel to start the car up. 

I fixed up the leak in the fuel filler pipe with putty(gas smell). The smell is gone but when I open gas cap, its suppose make pressure sound. First few fill up it made loud sound but now it only a hiss.

Back to on the lower gas mileage. Could it be the sending unit not the fuel pump? I read it on Nissan site that it gives incorrect fuel gauge reading.


----------



## rx7racr (Jan 25, 2004)

for what it's worth, I swapped out the O2 sensor, and my problem disappeared!! 

I didn't originally consider this because there were no codes being thrown...


----------



## MisterRx (Feb 8, 2006)

I was reading a 92 Sentra owner's letter on the web concerning poor gas mileage. He took his car to a mechanic who replaced Engine Module.

My question is what is Engine Module? Is it Ingition Module (Accord) ? 92 Sentra has IC Ignition Unit inside distributor is this Ignition Module? Does it have impact upon poor gas mielage?

Or is the main Computer?

What is Cold Start Sensor? Is it Engine Coolant Temperature Sensor?

Thanks!


----------



## wannaB13 (May 4, 2006)

get the darn car up on a dyno and do some low load testing. the dyno guy will have a wideband O2 if he is worth a $hit. Do a baseline and a power pull to make sure you are in check. If stock you should see 80-100 hp depending on altitude and relative humdity. After a cooldown for about 10-15 minutes, do some 50-70 mile per hour testing in your high gear. The wideband meter should be in the 14.7:1 range at crusing throttle. If you are anything like 13.8 or lower you are too rich and there is a problem somewhere like leaky injector, bad O2 sensor, bad coolant temp sensor, or a Junked out motor that just needs to be replaced or rebuilt. This is what I would do and I do it right. You can waste time and money by shooting in the dark and needlessly replacing parts or you can find the cause by doing some trouble shooting. I would start by the dyno session and somebody with a few wrenches and a good brain


----------

