# Odd idle/starting



## GraySentra (Mar 22, 2011)

I have a 94 Sentra GA16DE with 136K miles. It's been a great car with few problems. Over the past six months it has developed a new problem which my mechanic can't seem to fix. Hope someone has an idea.

There are three issues that I notice:
1. It has a slightly rough idle. Nothing crazy, just a slight odd miss. Everything is fine and then there's a slight blib and back to fine. Gives a slight shake when it happens.

2. It does not start as well as it used to. Usually fine when cold but takes extra cranks when warm. Sometimes it helps if I give it more gas pedal. Before the new starter almost sounded like it was not going to start.

3. Smells a bit like fuel or exhaust when I park it sometimes. Could be that there's a hole in the muffler, but that's been there for years and wasn't a problem before.

The car runs fine otherwise and still getting good mileage.

The mechanic has cleaned or replaced the PCV, replaced the starter with a new one, replaced spark plugs and wires, checked all vacuum hoses, and cleaned injectors. Battery is fine.

My suspicion is possibly the fuel pump is going. Does that sound right? Although I believe these tend to go quickly rather than slowly. Or maybe something is still wrong in the vacuum lines. Your thoughts?


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## jdg (Aug 27, 2009)

Same old story, half a tune up, half old parts.
What about the distributor cap and rotor?
Any codes?
Did this "mechanic", as you call him, check the fuel pressure? Gas cap seal integrity? Any checks done on the EVAP system at all?


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## GraySentra (Mar 22, 2011)

Thanks for your reply. Here's what the shop did. They are reputable and give a 24month/24K mile warranty on everything they do. Haven't had a problem before this.

First visit:
Originally had code 32 EGR. 
Mechanic tested EGR valve and checked OK.
Tested transducer valve = failed. Replaced.
Replaced EGR control valve and cleaned EGR passages.

Second visit (2 months later):
No codes.
Replaced starter. (claimed it was "sticking in the flexplate causing the engine to bump")
Replaced distributor cap/rotor.
Replaced ignition wire set.
Replaced spark plugs.
Fuel control tune up - clean fuel delivery components and perform fuel pressure test.

They do not mention the gas cap seal integrity so don't know if they included that in the fuel pressure test.


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## jdg (Aug 27, 2009)

Sounds like it's time to change the crank position sensor...whether or not the codes tell you to 'cause the damn thing is just touchy like that.
And it's quite possible the distributor, which has in it what amounts to a sort of cam position sensor in it, another part of the ignition system, is going out intermittently, but that would more likely show up as a 'no start' rather than a crappy start.


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## GraySentra (Mar 22, 2011)

How challenging is changing the Crankshaft Position Sensor? It's a 5 speed if that makes a difference. I've done some searching but can't find much.

And WHERE is it? I have read both that it's on the transaxle and within the distributor (assume they meant cam sensor). Even read on one site that a GA16DE doesn't have a crankshaft position sensor.

Doesn't seem any easy or cheap part to find either.


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## LvR. (May 26, 2010)

> It's a 5 speed if that makes a difference.


vs 



> Replaced starter. (claimed it was "sticking in the flexplate causing the engine to bump")


and 



> They are reputable and give a 24month/24K mile warranty on everything they do


Me? - I would insist on the guarantee since they have demonstrably not fixed the actual problem and then immediately I would only change the "reputable shop" and then start looking at the injectors first - dirty? - connections bad/corroded?


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## jdg (Aug 27, 2009)

5 speed vs flexplate...
oooo....good catch!
Maybe they also changed out muffler bearing fluid too eh?


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## GraySentra (Mar 22, 2011)

Verbally they said the starter was hitting the flywheel not the flexplate. Paperwork says flexplate. From your comments I assume this is not possible.

Yes, I plan to tell them the problem is still there and have them fix it.


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## LvR. (May 26, 2010)

ITO engineering mechanicals:

The starter ALWAYS will either "hit" the flexplate (auto) or the ring-gear/flywheel (manual). The bendix has teeth machined in such a way that the bendix gear will mesh with the flexplate/ringear due to magnetic pressure in the solenoid and play in the bendix clutch assembly. So their "hitting the flywheel" comment is suspect imo since its actually supposed to................ and a reputable service dept will ensure they write exactly what was involved in any repair/work so that claims afterwards can be very easily argued/disputed.


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## jdg (Aug 27, 2009)

GraySentra said:


> How challenging is changing the Crankshaft Position Sensor? It's a 5 speed if that makes a difference. I've done some searching but can't find much.
> 
> And WHERE is it? I have read both that it's on the transaxle and within the distributor (assume they meant cam sensor). Even read on one site that a GA16DE doesn't have a crankshaft position sensor.
> 
> Doesn't seem any easy or cheap part to find either.


Crank sensor - in the bellhousing, almost staring right at you, about halfway down the front of the engine, piece of cake to change out. Not too terribly expensive.
Cam sensor (i.e. #1 TDC sensor) - in the distributor, generally a guy swaps the whole thing, but if the individual pieces/parts can be found, they can be swapped out if a guy is handy with tools and wants that kind of a PITA  . I'd change just the pieces/parts, but I'm weird that way. And, no, the distributor isn't cheap.

Download the FSM for the '95 Sentra/200SX linked below. No, it's not for a '94, but the pieces/parts locations/other stuff is close enough to make an educated decision on whether or not that section applies to the '94 model.


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## GraySentra (Mar 22, 2011)

Would starter "bumping the flywheel" cause a slight blip in engine idle?

So far only CPS I can find online are around $200. Only a couple places seem to have one for a 1994. 

I should also note that the new starter did improve starting quite a bit. It is only occasionally that I have the starting issue. It always starts. Just once in a while it takes more cranks than it used to.

Thanks for all the help.


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## jdg (Aug 27, 2009)

Doubt the starter is bumping the flywheel any longer. If it was, there'd be more damage.

CPS - ya, they're expensive...but...they've been known to work and not work at the same time. If you had access to an o'scope, you could put the 'scope on the CPS output and check it. A meter would only tell you if it's working or not...not how well it is working.

And the new starter? Well, maybe it was just 'that much' newer and spun the engine just 'that much' faster when starting to make the CPS work 'that much' better by putting out just 'that much' more signal to help the engine start or drew 'that much' less current while starting keeping the battery voltage just 'that much' higher...who knows...it's a crap shoot...


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## chrismariscal (Jan 10, 2011)

*Crank Sensor Location*



jdgrotte said:


> Crank sensor - in the bellhousing, almost staring right at you, about halfway down the front of the engine, piece of cake to change out. Not too terribly expensive.


Can anyone be a little more specific as to where the Crank sensor is? Or does anyone have a picture? Has anyone replaced it before? 
Or what is the bellhousing? 
Sorry for all the questions. Thank you!


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## smj999smj (Jan 1, 2006)

A 94 Sentra GA16DE does not have a crank position sensor, which is why you can't find it! The cam sensor is integral of the distributor, so you need to replace the distributor assy. to replace it. The "bellhousing" is the part of the transmission that bolts to the engine. The 1995 Sentra (B14) was the next model design, so the fsm for a 95 is quite a bit differant than the 1994 Sentra (B13), especially when it comes to powertrain control. It would be good for some mechanical information. If you suspect a fuel pump issue, then it should be tested using a fuel pressure test gauge. While at it, I would do a fuel pressure leakdown test to make sure there's not a fuel injector leaking down, which could cause a startability issue. An ignition issue such as a failing cam sensor could be checked with an oscilloscope, something that a good shop "should" have. I don't like "throwing parts" at a vehicle until it's fixed; it's a bad habit that gets expensive after a while! I would also consider getting some throttle body cleaner from the parts store and cleaning out the throttle body, taking it for a good ride, then checking the timing and base idle adjustment per the FSM procedure. Improper base idle adj. will affect the performance of the IACV-AAC valve, which is used to control fast idle cold start and maintain base idle after warm up.


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## chrismariscal (Jan 10, 2011)

smj999smj said:


> A 94 Sentra GA16DE does not have a crank position sensor, which is why you can't find it! The cam sensor is integral of the distributor, so you need to replace the distributor assy. to replace it. The "bellhousing" is the part of the transmission that bolts to the engine. The 1995 Sentra (B14) was the next model design, so the fsm for a 95 is quite a bit differant than the 1994 Sentra (B13), especially when it comes to powertrain control. It would be good for some mechanical information. If you suspect a fuel pump issue, then it should be tested using a fuel pressure test gauge. While at it, I would do a fuel pressure leakdown test to make sure there's not a fuel injector leaking down, which could cause a startability issue. An ignition issue such as a failing cam sensor could be checked with an oscilloscope, something that a good shop "should" have. I don't like "throwing parts" at a vehicle until it's fixed; it's a bad habit that gets expensive after a while! I would also consider getting some throttle body cleaner from the parts store and cleaning out the throttle body, taking it for a good ride, then checking the timing and base idle adjustment per the FSM procedure. Improper base idle adj. will affect the performance of the IACV-AAC valve, which is used to control fast idle cold start and maintain base idle after warm up.


Thanks for the reply. 
So i went ahead and bought a new *dizzy* and a new gasket. Found TDC and repalced the distributor. Now the car will start, sometimes- but then it will die out after like 3 seconds..  

Not sure if you have been following my story. It's a bad one. 
I picked up this car in december. It had been sitting for a few years, so right away i had to replace the **fuel pump*, **fuel filter*, **starter*, **alternator* and **new battery*. 
In January i did my full tune up- **Cap*, **Rotor*, **NGK Plugs*, **NGK Wires*, **O2 Sensor*, **Thermostat*, **K&N Air Filter,* **K&N oil filter*, and *cleaned my throttle body*. 
In February i had to repalce my **Alternator again*, **Front Crankshaft oil Seal*, **New Belts*, **Transmission Filter*. 
In March I put on new *Headers, *Cat Back Exhaust, and of course a sound system. 
And now.. 
In April i locked my keys in my car, in my driveway, with the car running. While waiting for the locksmith guy (30-45 mins?) my car started chugging real bad, shaking, sputtering, and a couple of times i thought it was going to cut out and die but it never did. I turned the car off once i got inside, and then it took like 5 try's before it would start. I grabbed my multi-meter and found that fuel injector on cylinder #3 died. Took the whole rail out, and **replaced all the fuel injector*s. MIND YOU I DID LOSE one of the fuel injector o-ring's, so i replaced it with one that looked similar. Anyways car still would not start. Checked and re-checked with other sentra's that i did not cross the fuel lines, i did not. Fuel pump is still good also. 
Next i replaced **spark plugs again*, and also **Fuel filter* again. Mind you this is *only 1200 miles* since i first got the car running! 
So i replaced the **Ignition Coil*. Nothing. and today i purchased a new **Distributor* which came with a new **cap* and **rotor*. But now it will start every other time, but doesn't stay on.  
I also tested my MAF and that is still good.

So. I heard that it might be that there is air in fuel system since i have repalced the injectors, but then on this forum i read that it's impossible for air to get in this car's fuel system, and that there is no need to bleed it because it bleeds itself. 
Or is it that because i didn't put in the exact same o'ring? 
Is this an issue that could be caused by my EGR valve? 

I have no idea, but i would really appreciate any help or ideas. I've been without my car for almost a month now. 
Thanks again guys.


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## chrismariscal (Jan 10, 2011)

or might it be a bad IACV? I haven't tested that yet. 

Also, i havent done the injector leak down test, only because i dont have the equipment. But from the top, there is no leak visible. And yes i know thats not as good and thorough as the actual test.


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## LvR. (May 26, 2010)

If you have a bad feeling about the replaced O-ring (as I do) I would suggest you yank the rails of the motor, and see if the injectors are at all leaking (or the O-rings) by pressurizing the rails while they are off the engine (switch on ignition but don't try and start the motor).

Alternatively - put a T-piece between the filter and rails and hang a fuel pressure or oil pressure gage off that ................. you should see the pressure stay around 40psi for many minutes after the ignition is turned off - if the pressure drops immediately you know you have a leak on the fuel system - injector/O-ring/fuel pressure regulator

I would start here because its currently a known suspect issue as identified by yourself


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## chrismariscal (Jan 10, 2011)

Will do. I'll replace all the o-rings probably tomorrow and post what happens.


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## chrismariscal (Jan 10, 2011)

replaced all the o-rings, tightened the whole rail to the proper torque. 

now the car starts every time, but only if i floor it, and the car will not idle at all. 

i cleaned the MAF, that helped. But next i will replace the IACV and the MAF, and hopefullt that will put my car troubles to an end. 
finally.


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