I'm having some stalling issues with a 97 Sunfire (2.2L) and need some other opinions before I go insane.

The main issue is the car will start and run fine for 15-30 minutes, then develop a slight stumble upon acceleration, then stumble a little worse, then finally stall completely. After that it will start but then immediately stall, and I can't really drive the car for another 2 hours or so. The stumbling and stalling happens a little quicker when it's hot outside, so I figure the issue is heat-related. Also, when this happens I usually get a P0171 code (lean fuel mixture), which I guess can be caused by any number of problems.

Several repairs have been made to try and fix this. Almost the entire fuel system has been replaced (tank, pump, filter, fuel lines, pressure regulator, etc.) except for the injectors. But from what I've read, a fuel problem will manifest itself at all times, not just when warm. All 4 cylinders have good compression. Spark plugs and wires have been replaced, along with both O2 sensors, and the crankshaft position sensor. Also have a new PCM.

I'm left with the coil packs and the ignition control module. Not wanting to spend $150 or more, I went cheap and got a used ICM but the problem still remains. Am I safe in assuming the problem is ignition related (either coil packs or module)? Are the P0171 and stalling-when-hot related problems? Am I missing something? Any advice will be much appreciated.

Its not the coil packs or the ignition control module cuz is not misfiring, I had the same problem
for me it was 2 fuel injector they were bad so I just replace them now it better ,
but than again it a 2.2 they sux, to many problems with those engine

I would test the fuel pressure when it wont start. Sounds completely fuel related, and that's what the computer is telling you, lean means not enough fuel or too much air.

I would think it would indicate rich if there was a problem with ignition, because unburnt fuel would be sent out the exhaust.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

Thanks for the replies. I guess I always thought a fuel issue would show up whether the engine was hot or cold. Any clues as to why temperature would matter, or what components would be sensitive to heat? I've read about vapor lock in other sites, but also that it's not very common in newer vehicles. When I remove the fuel cap (when the engine starts sputtering) I don't hear any loud hissing or anything, in fact there doesn't seem to be any pressure release at all.

Anyway, I don't see a Schrader valve to check fuel pressure- is there some other way to do it? Or will it have to be checked by a professional shop?

Why not just go buy haynes manual book for cavaliers (autozone) its only $20 and it very useful , and it tells you how to do it

Haynes Repair Manual for the Chevrolet Cavalier & Pontiac Sunfire for 1995 thru 2005 ((2.2/ 2200 OHV) (2.3 /2.4 /2.2 DOHC))has clear instructions and hundreds of photographs to help you perform anything from simple maintenance to basic repairs. Whether you're a beginner or a pro, you can save big with Haynes!

Complete coverage for your Chevrolet Cavalier and Pontiac Sunfire for 1995 thru 2005:
--Routine Maintenance
--Tune-up procedures
--Engine repair
--Cooling and heating
--Air Conditioning
--Fuel and exhaust
--Emissions control
--Ignition
--Brakes
--Suspension and steering
--Electrical systems
--Wiring diagrams

Ricky martinez wrote:Its not the coil packs or the ignition control module cuz is not misfiring, I had the same problem
for me it was 2 fuel injector they were bad so I just replace them now it better ,
but than again it a 2.2 they sux, to many problems with those engine

OK- I'm going to check the injectors tomorrow. My question is- wouldn't an injector problem show up with a trouble code like cylinder misfire or something else, besides just P0171 lean fuel mixture? Thanks.

I found this online
Check your (EAVP)

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop, the oxygen sensor inputs are added and used by the PCM to calculate Short and Long Term Fuel Trim (FT), fuel delivery adjustments. Short Term FT values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term FT values change slower in response to trends in Short Term FT adjustments. The fuel trim index is the average of Short and Long Term FT and purge learn memory based on engine speed and load. Fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, DTC P0172 sets.

Evaporate will throw evaporate codes. What about intake leak? Gaskets do fail...

Injectors replaced- problem persists. I'm now leaning towards a vacuum leak and trying some type of smoke test. My question is- why/how would heat affect a vacuum leak? When the outside temp is in the 90's, I get about 10-15 minutes of driving before it dies. When it's cooler, I can drive a little longer before the stalling occurs.

I get that extra air would cause the P0171 code, but I don't get how heat is involved. Any ideas would be much appreciated.

Vac leak would probably cause a high idle, not stalling and dying but if you want to check for a vac leak get a can of starting fluid and spray around the intake/throttle body and vac lines while the car is running. You will notice the rpms ruse if any fluid is sucked in through a leak. . I would check fuel pressure also. Your pump could be heating and malfunctioning once warmed up, and probably not functioning correctly when the car is running.

Jordan wrote:Vac leak would probably cause a high idle, not stalling and dying but if you want to check for a vac leak get a can of starting fluid and spray around the intake/throttle body and vac lines while the car is running. You will notice the rpms ruse if any fluid is sucked in through a leak. . I would check fuel pressure also. Your pump could be heating and malfunctioning once warmed up, and probably not functioning correctly when the car is running.

I was afraid the fuel pump might be an issue. I have a fuel pressure tester, but it's for vehicles with a Shrader valve. This car doesn't have one- how do I check fuel pressure without a Shrader valve?

No clue... never had to do it. But you can also spray starting fluid in the intake when it dies/ wont start and see if it will run off the fluid