YACT: Car stalls after starting

[brtspears2]

99 Chevy Malibu LS with 3100 V6, 72.5k miles.

On warm starts the car will start much slower and will stall out. The engine will start, rev to a bit over 1k, then slowly make a dive down to 0. If I give it some gas, it will stay alive. No lights are on at all. I asked a "friendly" local mechanic to look, he says I need a new PCM and a new idle air sensor.

Otherwise the car runs excellent when it gets started and moving. What could be wrong? I did replace the alternator a last week and the voltages are in spec.

 

[vshah]

well maybe what could be wrong is the PCM and idle air speed sensor.

 

[Mr N8]

Definitely a flux capacitor.

 

[brtspears2]

Originally posted by: vshah
well maybe what could be wrong is the PCM and idle air speed sensor.

Thanks for that input. But could there be anything else that could be causing this.

 

[Quixfire]

I could agree with a idle air control valve (IAC), but I haven't heard of a idle air sensor. As for the PCM replacement I would think you could get your local dealer to reflash the original PCM to resolve the concern.

But if you are handy with some minor car repairs you could try to clean you IAC valve and throttle body plates yourself to see if that would resolve the problem.

 

[xXped0thugXx]

Originally posted by: Quixfire
I could agree with a idle air control valve (IAC), but I haven't heard of a idle air sensor. As for the PCM replacement I would think you could get your local dealer to reflash the original PCM to resolve the concern.

But if you are handy with some minor car repairs you could try to clean you IAC valve and throttle body plates yourself to see if that would resolve the problem.

get a toothbrush and some carb cleaner and go to work, sometimes built up gunk restricts the flow

 

[brtspears2]

Cleaned IAC and PCM got reflashed by Chevy dealer. Still stalls only on warm starts. What else could I try? I've done all the maintaince according to the manual.

 

[djplayx714]

check your grounds and your spark plugs. i had the same problem recently that turned out to be a weak/near death battery.

 

[TechnoKid]

Chevy uses MAF senors right? Have the MAF measured on an ohm meter, I think you can start the car with the MAF dissconnected, but it will throw a code. If the MAF is failing, or is heatsoaked, that may be the problem right there. You can try cleaning the MAF sensor in pure solvent, or, buy a can of electronics parts cleaner (QD electronics cleaner is what I use) and try cleaning the MAF.

 

[stonecold3169]

Does it start at 1k, and then drop a lot, go back up (not all the way to 1k), drop some more, go back up again not quite as high up, and so on? Might be an oxygen senser

 

[brtspears2]

Originally posted by: stonecold3169
Does it start at 1k, and then drop a lot, go back up (not all the way to 1k), drop some more, go back up again not quite as high up, and so on? Might be an oxygen senser

More like start, goes to a little below 1.5k, and keeps going down from there to 0. If it helps, when the OBD codes are checked, there are none.

 

[Thegonagle]

I'm guessing that you DON'T need a new PCM. That's big money for you, and a large profit for an unscrupulous garage hack. When in doubt, as you should be, take it somewhere else.

 

[Thegonagle]

Oh, and send a PM to Marlin1975. He's quite an expert on GM cars.

 

[cheetoden]

Sounds like a IAC(idle air control). Pretty easy to do yourself.