fpena944

This problem has really been irritating me lately...

In the morning I start my car and it starts just fine, no problems whatsoever. However in the afternoon (keep in mind my car has been now sitting for 12+ hours but since it's later in the day the temperature has increased significantly) the car will start but the "Check Engine" light is lit.

So at this point the vehicle runs really rough and the exhaust smells overly rich. Usually just by running the car for a couple of minutes it will correct itself, but other times it will buck and hesitate quite a bit when I give it gas. Under this condition it searches for idle going back and forth from nearly 0 to 1000 RPM. At times it cannot handle this so it just dies. When this happens I am able to start her right back up though.

I went ahead and took apart the AFM last week and re-grooved it but it didn't seem to help at all. I don't think it's bad gas since I've been having this issue for about the past month. Fuel filter has been changed, air filter changed, oil changed, etc.

Anyone have any idea what might be the cause of this? It's bugging me!!!

Thanks!

fpena944

Just an update...

This morning the "Check engine" light came on briefly (it was somewhat warm this morning) but after about 5 seconds turned off and the car ran just fine.

Anyone have any ideas?

JustinL

Watch your oil pressure and voltage at start up. That might give you a clue where to start a deeper investigation.

HTH
Justin

fpena944

Both the oil pressure and the voltage seem to be within normal operating range.

The oil pressure of course moves slightly as the car hunts for it's idle position but the voltage meter stays above 12 (until it dies that is!) plus all electrical components work even once the car dies.

JustinL

How do your plugs look? Might be worth pulling them and checking if there are any obvious problems there. Does it still rev and drive ok once it gets going?

fpena944

Plugs were replaced about 10k miles ago, the wires are still the old set but fit very snug over the plugs and visually seem to be okay.

Once the car gets running it performs very well, which is what makes this problem all more confusing. It's just that initial startup phase that causes it to stumble. It's almost as if the vehicle needs to have the "cobwebs" cleared and once it's done it works perfectly. Ugh...

JustinL

Hmm, that is interesting. I'm stumped. Voltage and Mechanical stuff works fine after it warms up, but the "!" light is on for a few minutes at start up. Are there any other lights lighting up on the console? Like maybe the alternator light on the volt meter? Usually something else comes on with the "!"

Sounds like an electrical gremlin to me... maybe Iceshark or someone can help you diagnose it further. You could replace the Cap and Rotor, but I doubt that would solve the console light.

Sorry I couldn't be of more help,
Justin

MHT

if you can, check the resistance of the coolant temp. sensor before you start it in the eve. see if the reading makes sense. At room temp the sensor should read approx 2,000 ohms, I suspect the resistance will be much higher, possibly even an open circuit. If the resistance is real high the computer will dump a lot of fuel and the car will not run well, high resistance = cold temp. When you say check engine, I assume that you actually mean "Check Engine" and not the "!" light.

JustinL

Do we have "check engine" lights? I've never seen it. I just assumed that's what the ! was. Wow maybe I was way off.

fpena944

MHT,

Your theory makes perfect sense! One thing I failed to mention is that I occasionally have the "jumpy temperature gauge" issue from time to time where the water temp gauge will show the vehicle overheating one second then move back down to normal temperature the next second. (freaked me out the first time but I pretty much ignore it now)

Anyway, I did a search on the archives and couldn't find much information on checking the resistance on the Coolant Temp Sensor. Is this sensor the one in the block for the engine temperature or the one in the radiator that turns on the fans? Which terminals do I check resistance on?

JustinL - Yeah our cars have a "Check Engine" light on the Volt/Oil Pressure instrument cluster. It's towards the bottom center. Be glad you've never seen it!

Thank you both - I hope I can get to the bottom of this soon!

fpena944

Bumping it up - can anyone answer the question about the coolant temp sensor for me?

fpena944

I know this is an old thread but for the purpose of archiving I thought I should post the solution so someone else can use it for future reference.

The problem I described ended up being corrected by replacing the fuel pressure regulator. The car got really bad towards the end, where it was even difficult to keep it at idle. But in any case, she runs like a champ now!

fpena944

Guess I spoke too soon...

Car ran great for a couple of days. It would start up without any problems and would run just as it used to. But the problem is back once again. Let me review once more:

When I start the car up (now it doesn't matter whether it is morning or afternoon, it happens probably 90% of the time) the car's "Check Engine" light is on and it runs really rough stumbling from about 100 RPM - 1000 RPM. The exhaust smells rich and the idle just hunts from high to low. If I let it go for a while it eventually dies and I have to restart it.

Normally to get past the problem I let it idle for a couple of seconds and keep my foot lightly pressing the accelerator so that it stays at about 1000 RPM. After making sure the engine has enough oil running through the system I rev the car up to about 3000 - 4000 RPM a few times and the check engine light goes away. So at this point the car is usually running as it should and I have no problems.

Occasionally however the car will revert back to it's "Check Engine" status after I slow down at a stoplight. Here's where it gets dangerous because I can't really accelerate as I should with the car in this condition.

Now keep in mind when I replaced the fuel pressure regulator I also replaced the DME relay so let's assume that's out of the picture. I also checked all the O-rings on the injectors when I removed them and the car had it's plugs changed about a year ago. I don't think it's the gas being used since the problem began when I lived in New Jersey and now continues in North Carolina.

Anyone have any ideas? Or am I going to have to give in and send her away to a mechanic?

Luis de Prat

So fpena944, did you get this resolved by cleaning the Idle Stabilizer Valve, after all? My S2 is having similar symptoms and I'm not sure where to start!

BTW, did you ever replace the ignition control module on this car?

fpena944

Hi Luis,

I didn't get a chance to tackle the vehicle this weekend. I'm ordering some brake rotors soon so I figured I'd wait for those to arrive so I can just take care of all maintenance at once.

It's still doing it though. It won't do it first thing in the morning when the engine is cold, but any startup after that, I get the stumbling. The fuel injector theory is almost making sense at this point.

In any case as far as I know the ignition module has not been replaced. But don't you think the issue would be a bit more intermittent if that needed to be changed?

Any luck with yours?