Hi,
I have a 2003 MC with 62K on it. It starts after a few cranks but if you take your foot off the gas it stalls. Additionally twice while driving it was idling so high that the car would go about 40 mph without stepping on the gas. The car is at my mechanics now. Oddly no check engine light has gone on. Anybody have any idea what is causing this. I am suspicious of the IAC. Thanks

 

My mechanic replaced the IAC and the car seems to be back to normal again. There is one more small problem I would like to remedy however. When I start the car it cranks for a couple of seconds and I usually have to give it a little gas or it stalls. Once you idle it up with the pedal it is fine. I have had it to the mechanic 2 times, and of course both times he could reach in through the window and it started right up as it should. Most of the time it will not start as most cars do. It should start properly every time.
Anybody have any ideas as to what causes this?

 

I would suggest cleaning the throttle body and MAF. If the pintle of the IAC was that dirty I would bet the TB and MAF are too.
Which motor do you have?

 

I have the 3.1l Car runs beautiful when driving. The starting problem is not really that bad, but its not right either. I had a 1996 MC before this and except for changing the intake gaskets twice that car was nice. Still have the 96 and it still starts with a touch of the key. Had to take it off the road because the rear crossmember is rotted and ready to break.

 

OK. A common problem with 3.1 and 3.4's is blockage of the passage in the throttle body where the EGR connects to it. Carbon builds up in the port and needs to be cleaned by scraping out the carbon from the inside of the TB after removing the air duct and screen, and using mechanics wire to ream out the passage from the outside. The problem will eventually throw a EGR flow code when it gets bad enough.

Here's some instructions ofn how to do it:

1. Video:
2. Illustration and description: http://easyautodiagnostics.com/gm/3....nostic-tests-2

 

Thank you. A couple of months ago the mc threw a p303 code. However the car was running fine. I took it over to my mechanic and he checked the coils, plugs, fuel pressure, throttle body, maf. He said everything was fine. The car has not thrown any codes since, not even with the latest idle problems. Thank you for your advice, I will definitely get that done.