I have a 1996 Monte Carlo with a 3.1 V6. The majority of the time it runs fine. Several years ago it started dying when the car was being driven at low speeds when the engine was idling It always started right back up. Most recently it does one of two things when it starts up every 5th or 6th time. It either revs to 3,000 rpm then dies or it will crank over and over and not start. If I let the car sit for some period of time it will start up as if nothing ever happened.


It has been taken to several shops and it doesn't through any codes. I have changed the fuel pump assembly, fuel filter, fuel relay, fuel pressure regulator, mass air flow sensor, manifold pressure sensor, idle air control sensor, throttle position sensor, ignition coils, ignition module, spark plugs, spark plug wires, checked the alternator and it has 14.4 volts under load, replaced the battery, check the PCM and the connectors look good. I have removed and cleaned grounding points on the engine block.


Only light of code of any kind that comes and goes is the volts light on the dash. When the engine revs to 3,000 it comes on. Otherwise it never comes on.


Open to any suggest someone might have.

 

I had this happen on my 99 Grand Prix and it was the Mass Air Flow sensor. Changed it twice because the one I bought brand new was bad.

 

As P343 mentioned, the MAF could be bad, but a good shop should have been able to see that with a decent scan tool capable of reading grains/sec. flow. I would also be suspicious of the upstream O2 sensor, dirty EGR valve &/or clogged EGR port where it connects to the throttle body, or a clogged cat., all of which should be detectable with good scan tool data interpretation.

 

My initial thoughts are a clogged EGR passage (the old 3100's had that happen pretty commonly), clean the passage way for the IAC or an upstream O2 sensor (pretty much what Plumbob said). That is just the ideas from the gut based on what you described.

The car might not throw any codes because it believes it is doing what it should based on data it's getting (even if that data is wrong).

 

Thanks to everyone that posted feedback. I cleaned the EGR port. It had a small amount of carbon. I also inspected the EGR valve and it open and closed. Was not sticking. I also replaced the upstream O2 sensor. When I was putting the throttle body back together I poked my finger on the throttle cable. On closer inspection I noticed it was frayed where the cable came out of the plastic sleeve. I am going to order another one and see if all these fixes make a difference. Ii maybe I am chasing two different issues. The frayed cable may be the cause of the higher rpm at startup that happens occasionally. Don't want to drive it until I get this replaced.