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2001 Monte Carlo stalls after the car is warm


MikeGrooms
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Hello, I have a 2001 Monte Carlo that when cold, will start with a simple turn of the ignition key. Once the car is warm, say driven 8 miles and turned off, I am unable to get the car to start without hitting the gas petal while turning the key, otherwise it simply stalls over and over. I have not had this problem in the past and was wondering if anyone may have any idea as to what may be the problem. There are no warning lights or error messages at all. The battery is brand new as is the negative battery cable. Please let me know if anyone has had a similar problem and if there are any possible ideas as to a solution. Thank you for reading!

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I know this car, and the owner. The engine is an L36, a better question is what's been done so far? I know there's been a bunch of stuff tried so far, but I can't remember what.

Matt and Nas suggested fuel injector problems in the intro thread but it seems fishy that 6 of them would have heat soak problems.

I'm thinking Crank Sensor or maybe an ICM, I should have L36 injectors if you want to try them.

Edited by Imp558
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Problem hot sound like either a failing ICM or Fuel Pump. Change when pressing on accelerator tend toward the fuel pump. First thing should be a pressure gauge on the fuel rail and see what the cold and hot start pressures are.

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The fuel pump is brand new. The engine is stock, nothing modified. The dealer seems to think it has something to do with the after market stereo (subs and 2 amps) that run off a separate battery. I removed the fuse for the stereo and that does not seem to matter. The battery is brand new as is the negative terminal cable. It is hit or miss, sometimes it stalls after being warm and sometimes it does not. I have had the car since 2006 and never once had a problem until recently. The stereo was put in in 2007 and has never caused a problem. They seem to think it may be an electrical problem. I do notice that the volt meter on the dash fluctuates when it is in "stall mode", for lack of better terminology. 

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A few thoughts on things to check.

 

Connect a fuel pressure gauge and see how fast pressure drops off after the car is shutdown, if it falls like a rock you may have a fuel pressure regulator issue. Also pull the vacuum line and check for fuel in it.

 

Unplug the MAF sensor and see how the car behaves

 

While the car is running remove the oil fill cap and see if the engine wants to pull vacuum through the crankcase. If it does you may have a PCV issue.

 

Have the intake gaskets ever been done? Upper intake ever replaced?

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The fuel pump is brand new. The engine is stock, nothing modified. The dealer seems to think it has something to do with the after market stereo (subs and 2 amps) that run off a separate battery. I removed the fuse for the stereo and that does not seem to matter. The battery is brand new as is the negative terminal cable. It is hit or miss, sometimes it stalls after being warm and sometimes it does not. I have had the car since 2006 and never once had a problem until recently. The stereo was put in in 2007 and has never caused a problem. They seem to think it may be an electrical problem. I do notice that the volt meter on the dash fluctuates when it is in "stall mode", for lack of better terminology. 

 

As someone who has cars with aftermarket stereos, a sound system would not cause your engine to stop running. You'd fry your alternator before you'd fry your fuel delivery system or ECM. That's someone incompetent working on your car. That's like a dentist saying the reason your tooth hurts is because you have a cut on your hand.

 

Anyways, the volt meter will fluctuate when you try to start it repeatedly because you're draining the battery as you keep cranking. That's normal, but has nothing to do with your add ons.

 

Also, Imp mentioned that he would find fishy that all 6 fuel injectors would get heat soaked but my 89 Regal only had 2 working injectors. There is a possibility that all 6 can be bad but highly unlikely in a 15 year old car. It is possible for one or 2 to be bad and cause the car to stall when warm, but I would use a multimeter and test the injectors that way before removing anything on the engine. Luckily on the 3800, it's easy to see all 6 injectors.

 

I would suspect the ICM and coils if the car idles rough when it does run. I had that issue with my 94 Cutlass that it would get 10mpg and it was a bad coil causing it. If that's the case, I would replace the whole setup (ICM and coils). Easiest way to find that one out would be to remove the whole assembly from another 3800.

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I have the car at the dealer. They are telling me the reason it is stalling is there is a crack in the intake manifold (still waiting to find out if it the upper or lower). They want $1,300 to fix this. Anyone ever replace these before? How extensive is the job? Please let me know if anyone has any information on this. They say the vacuum leak in the manifold is causing it to stall. Thank you!

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First thought is someone needs a boat payment.

 

Usually a crack/leak in an intake manifold will result in a high idle as the computer tries to compensate for excess air. Stalling is more likely a failing ICM, bad TPS, sticking IAC, or low fuel line pressure. Which will require instrumentation.

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I have the car at the dealer. They are telling me the reason it is stalling is there is a crack in the intake manifold (still waiting to find out if it the upper or lower). They want $1,300 to fix this. Anyone ever replace these before? How extensive is the job? Please let me know if anyone has any information on this. They say the vacuum leak in the manifold is causing it to stall. Thank you!

 

Just did that job, total cost was under $250 in parts.

 

Its a common job that basically every Series II 3800 will need at some point

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I have the car at the dealer. They are telling me the reason it is stalling is there is a crack in the intake manifold (still waiting to find out if it the upper or lower). They want $1,300 to fix this. Anyone ever replace these before? How extensive is the job? Please let me know if anyone has any information on this. They say the vacuum leak in the manifold is causing it to stall. Thank you!

 

Pretty simple job. This would be the same as changing the gaskets from nylon (plastic) to metal when the plastic ones fail. The only difference is that you would be bolting on a new intake instead of using the old one.

 

The job would take about 4 hours, give or take.

 

More than likely, your upper intake manifold cracked. It's made of plastic.

 

I have a metal upper intake from a Series 3 if you want. You would have to get an adapter to get the throttle body to work however.

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if it's got 150,000 miles on it I don't see a problem with doing an intake manifold plenum, it's something like seventy Thousand Miles overdue. what's confusing is that there is a vacuum leak and it should be a coolant leak with a typical failure

Edited by Imp558
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