# B12 #2 Yes!!!!



## SuperSentra4203 (Dec 17, 2002)

Well guys, I'm back again. Life sucked with the POS (Grand Prix) 15mpg, 'nuff said. A slow tank, 'nuff said. I got top love it a little though, as friends wanted to do a 3.1L Turbo swap. One day at my girlfriends house, a huge storm rolled through (one of many this year) and the end result was my interior submerged in 10 inches of nasty water. My buddy who finally has 10 grand in his 70 Monte Carlo (for details just ask) loaned me the $250 for my new Sentra which I found sitting in an impound lot in the boondocks. Looks like hell because of rust (it's black) but no accidents, plus newer motor/tranny/clutch/CV joints. Man does this motor roar (muffler looks like a blocks of swiss cheese).
My girlfriend has gotten to love the B12 and is looking for here first car, she better buy a Nissan or else I sold the Grand Prix for $100 just to get it outta my sight. I never want to be in another GM products again. Every one I have been in or driven, I wanted to put it in a lake!!!!

Meanwhile, the B12 has only has one problem, if the motor isn't fully warmed up, it wants to die out but idles at about 500rpm and will eventually stall. I think it's just ignition since it had a new cap/rotor installed. Also, I have a air/fuel ratio meter. I now know at idle it runs extremely lean, but I give it gas it'll richen up and lean out, then richen up and then lean out. It goes back and forth. Any ideas, the O2 sensor looks new, think it may be the AFM going out??? Something is keeping the A/F ratio from being ideal. It's either rich or lean, but very lean at idle to clear things up a bit.


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## AVERAGE (Aug 9, 2002)

sup man glad that ur back. sorry to say that i have fallen off the b12 wagon myself with the new love of my life, my 88 b6 323.i still have 3 , though


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## SuperSentra4203 (Dec 17, 2002)

Hehe, the 323 is Mazda's version of the B12/B11. Just as the Mitsu Mirage and Toyota Corrolla. All great cars. I wish I had one of each, but I'll take my B12 over any car, any day, and i'm not joking. Getting back in another B12 was awsome!!! My buddy bought it just to see me pull off the good 'ol 6800rpm shifts and being happy.

BTW, how much for the body kit? I also need front fenders, a trunk lid, hood. Heck, find someone who has rear quarter panels that I can tack weld on, too. Right now, my buddy is willing to help pay for a CA18DE swap. Already found the motor, complete harness and ECU. Just need cash. Had a temp job, but I was fired.


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## Mervic (May 1, 2002)

I think your right on guessing it is your MAF.


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## SuperSentra4203 (Dec 17, 2002)

Or in the B12's case its a AFM (Airflow Meter) Darn $190 dealer parts. Hope it doen't get so bad it causes a 3500rpm rev limit.


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## fastpakr (Sep 18, 2002)

Running lean at idle and oscillating back and forth (at roughly 1 hz) is completely normal. It does go somewhat rich under a load and at WOT, correct?


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## SuperSentra4203 (Dec 17, 2002)

Correct, but it will also run pretty lean at WOT as a few thousand rpm increase. Is it just the design of the ECU to cut down on emissions and save fuel? I take it that is why it runs lean at idle. Just seemed really weird because I know a few friends that run AFR gauges and they don't do anything like how my car acts. Now that I really think of it, the only power difference I feel as it drops out of the torque band and before the horepower band.


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## Crazy-Mart (Jul 14, 2002)

try to adjust the TPS sensor ... you know it as a idle switch in it ??
probably it doesnt go in idle mode when you release the gas... and it normal the AFR doesnt read to much on idle since it getting colder ... have you check for vacuum leak ?? or clogged vacuum lines?? this could make fluctuation on the gauge ... if you want to make sur it read out correct do a WOT run and check it... should stay all they way at around 1/2... another thing to check too... prestone !! is it filled correctly ?? the temp sensor need the right value to inject the right amount of gaz... maybe its shorted or stuck with shit over it !! 

Good to see you back !


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## Mervic (May 1, 2002)

SuperSentra4203 said:


> *Or in the B12's case its a AFM (Airflow Meter) Darn $190 dealer parts. Hope it doen't get so bad it causes a 3500rpm rev limit. *


 Sorry to correct you but all Sentra and Pulsar uses MAF (mass air flow). The only one that uses AFM (Air Flow Meter) is the E15Et. AFM measures the amount of incoming air buy using a sensor flap, while MAF uses heated wire or film to measure air going in.


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## fastpakr (Sep 18, 2002)

Mervic, what you're calling an AFM is the same thing as a Vane Air Meter, right?


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## minute rice sentra (Mar 21, 2003)

the E16 does not have a MAF, it has an AFM.


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## SuperSentra4203 (Dec 17, 2002)

Mervic said:


> *Sorry to correct you but all Sentra and Pulsar uses MAF (mass air flow). The only one that uses AFM (Air Flow Meter) is the E15Et. AFM measures the amount of incoming air buy using a sensor flap, while MAF uses heated wire or film to measure air going in. *


Wrong, the GA16i uses a AFM (Airflow Meter) Pretty much just like a MAF though, but the only real difference is a MAF is between the air filter and throttle butterfly.
Good news guys, Trusty Rusty is running great. At WOT, it runs rich or almost ideal, no matter what rpm it's at. I adjusted the idle also. I have been thinking what you have been Crazy. The coolant temp sensor. The GA16i uses this as the main sensor to keep a good idle and amount of fuel to inject. My old B12 had a bad one and would always idle at 2000rpm or more. I knew the coolant was bad since I got it, hell, it was orange. No, it's not Dex-Cool. Just really bad coolant. Since i'm going to run down the quarter about 5 time tommorrow, I have made sure every vacuum line isn't damages. I cut a few ends until they weren't split and put them back on. My gas milage has increased (I drove about 200 miles today) 
BTW, the GA16i doesn't have a TPS, the GA16DE does. Or does my repair manual forget to mention it and I just can find it. Anyway, My idle is good when it's hot, so that tells me the coolant does need flushed to correct this problem. Also, the fluctuation at constand throttle/speed is supposed to happen. A mechanic told me on non-OBD I & II vehicles, the O2 sensors aren't designed to send a constant signal, which accounts for the fluctuation.
BTW, I'm very happy to be back!!!:banana: :jump: Driving that stupid Grand Prix was driving me nuts!!!!


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## Mervic (May 1, 2002)

I got my info in the Chilton manuals and it did say that only the E15Et uses the AFM. And to correct you again, the GA16i does have a TPS sensor. And the E16 also uses a MAF not AFM. Where your getting all your info?


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## Crazy-Mart (Jul 14, 2002)

all cars got TPS  at least the one with electronic fuel injection


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## minute rice sentra (Mar 21, 2003)

Got my info out of my factory service manual for my '88 E16i.
the haynes manual agrees with me too and says that MAF meters were on mpfi engines and AFM is on TBI engines.


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## nastynissan (Jan 26, 2003)

Sorry Mervic.... Gotta agree with everyone else..... Ive had 7 Sentras from 87 to 92 with every engine, tranny combo available (from the factory that is)... Minute rice and Crazy are right... OF COURSE..... There have been exceptions to the rule before.... And Manuals have been WRONG before.....


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## minute rice sentra (Mar 21, 2003)

yeah, i don't rely on my haynes too much anymore since i got my FSM, becuase there are so many details that have been overlooked and the FSM is specific to my exact year.(no details left out)


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## SuperSentra4203 (Dec 17, 2002)

Crazy-Mart said:


> *all cars got TPS  at least the one with electronic fuel injection *


That's what I thought, but I can't find it. Ehhh, just better look harder. 
Mervic, AFM's and MAF's are almost the same, besides the location and what they measure. Kinda like ECM's and ECU's, same thing, just pretty much a different name. 
Hmm, all the talk about FSM's makes me want to go get one.
Crazy, the coolant flush helped a bit, but the idle still want's to die is the motor hasn't been run for 10 minutes. I'm pretty sure it's the ignition timing. Didn't make it to the strip, stupid rain storms. I HATE OHIO WEATHER. IT NEEDS TO MAKE UP IT"S MIND!!!!


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## fastpakr (Sep 18, 2002)

SuperSentra, what kind of sensor are you calling an 'AFM', i.e. what specifically is different about it from a mass air sensor? The location certainly doesn't make it a different type.


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## SuperSentra4203 (Dec 17, 2002)

Okay, let me clear this up, most manuals call it a AFM, but I tried to get one from a dealer and they had no clue what it was. It is actually called a Mixture Modulator Sensor in the dealer manuals.


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## Webfoot (Apr 24, 2003)

Mervic said:


> *Sorry to correct you but all Sentra and Pulsar uses MAF (mass air flow). The only one that uses AFM (Air Flow Meter) is the E15Et. AFM measures the amount of incoming air buy using a sensor flap, while MAF uses heated wire or film to measure air going in. *


Uh, maybe we ought to find out what kind of mototr we have here. My E16s has a carb. air/fuel meters not used. And it has the same symptoms/problem as SuperSentra4203.


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## SuperSentra4203 (Dec 17, 2002)

I've concluded that my ignition timing is off. It also pings like crazy under load at low rpms (2500 & under), has enough fuel, new plugs/wire/coil, and that's on 94 octane. 87 sounds like a diesel.


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## fastpakr (Sep 18, 2002)

So how does it physically operate, i.e. is it a heated wire sensor, vane air sensor, or what?


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## SuperSentra4203 (Dec 17, 2002)

It just has a 'plug' that protrudeds into the TB. Think of an O2 sensor. Works pretty much like that.


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## fastpakr (Sep 18, 2002)

Sorry, but that isn't nearly enough information to be useful. How many wires? Is the sensor that protrudes into the TB heated? Your information so far isn't helpful.


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## SuperSentra4203 (Dec 17, 2002)

I know it hasn't been very helpful, I know this. Here is what I have one it. Dealer reference # 16078, part # 16078-84A00 Listed as a Modulator-Hot wire. I do believe it has three wires. It's a heated wire sensor as far as I can tell. I'll rip my TB apart as soon as it stops raining to clean it and get back on the specifics of the sensor.


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## fastpakr (Sep 18, 2002)

No, that's enough. It's just a MAF sensor then - a slightly different form, but still a MAF sensor.


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## SuperSentra4203 (Dec 17, 2002)

well yes, your right. But the actual name isn't a MAF, some people that aren't aware of this might have problems and spend hours looking for a MAF. The AFM can only be seen if the intake is taken apart.


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## fastpakr (Sep 18, 2002)

It's different from a normal MAF sensor in how it's placed, but functionally that's exactly what it is. Whether Nissan chooses to call it an AFM or a MAF sensor it's still using a heated wire to measure air mass through current regulation.


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## SuperSentra4203 (Dec 17, 2002)

Okay, you seem to know quite a bit about MAF in general. Would this cause my horrible idle when the motor is cold? It want's to die out unless the motor is totally warmed up.


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## fastpakr (Sep 18, 2002)

I doubt it, as far as I know the MAF should come online instantly, not like a heated O2 that takes several minutes of warmup before it can provide good data. I'll admit I haven't read this entire thread closely, and I'm more used to Ford fuel injection systems.

Have you tested the coolant temp sensor? If you have a factory shop manual it will probably have a table of the electrical readings it should provide at given temps, and can be tested on the stove in a pot of controlled temp water. Same should go for the air temp sensor. What about fuel pressure and timing? Is the base idle set properly?
I don't know how the data output of a Nissan MAF works - everything I use has MAP based EFI. Is the output frequency or voltage based? Like the other sensors, if you can find a table of the proper specs, you should be able to test it as the car warms up. If the data is in spec at the sensor, test it at the input pins to the ECU. What does a '90 Sentra give you in the way of computer diagnostics?


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## SuperSentra4203 (Dec 17, 2002)

I was told it was the AFM/MAF by many people, mechanics, dealers, etc... The O2 is new, as my A/F meter works great. I am going to pull the coolant temp sensor soon to test it. I think that is the problem. I flushed my coolant system and it has gotten better, so it seems to me the sensor is clogged. Manuals says it's a "wax-packed servo" I take it the wax gets heated by coolant ans expands, lowering the idle. Should be a cheap part.


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## fastpakr (Sep 18, 2002)

Good luck!


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