2002 Envoy problems with stalling and high idle

I have a 2002 4WD GMC Envoy SLE that has had several problems in the past three months. I’ll be at a stop light and the RPM jumps up to 1200 then down to 400 then up to 1000 then down to 200 and then it finally stalls. I can be at a stop light and the car will jerk forward which causes me to apply more pressure on the brake. Then I notice the RPM jumps up to 900 – 1200 as if the gas pedal is being pushed on. It continues to do this until I turn the ignition off. Sometimes when I coast in traffic and then press on the gas, the car hesitates for a second and sort of jerks forward.

It's been hard for my mechanic to diagnose the problem as the service engine light doesn't always come on. When it does, I take it to the shop and the mechanics fix the problems associated with the errors. I've had the throttle body cleaned, new air filter, new fuel filter along with a flush of the fuel lines, new spark plugs, as well as a tune-up.

After all this work, the car ran fine for a few days then all of a sudden the same problems have crept up again. The service engine light came on after the car was restarted due to a stall but then went out by the next morning. I'm tired of taking my car to the shop every week. What can be causing these problems?

Thanks for any help</SPAN>

Check all the vacuum lines for leaks. I'm no mechanic but that's the first thing i'd do.

check for codes if engine light is on possb cause is idle control motor called an iac

I have the same problem in my 2003 GMC Envoy XL SLE. I just noticed the problem about a week ago and as of now the problem is intermittent. Usually after stopping the car and shutting down the engine the problem will go away. Sometimes it stops for a few minutes, other times it stops for a few days. I am completely clueless as to the cause. Any help would be appreciated.

Thanks

There are many software updates for similar idle speed/control issues. I would suggest to both of you let a dealer look at these issues.

Vacuum leak (unless a TSB exists)

Loping idle is vacuum leak. 30 year old lawnmower, or a new car on the lot. If it sucks air where it ain't supposed to, it lopes.

Brick on pedal, block TB arm, anything to get a STEADY idle. 1200rpms or so... Feed starting fluid spray, A LITTLE AT A TIME, EVERYWHERE. Rev increase is the leak.

In a tough spot to pinpoint? Light a book of matches, blow it out while the heads are burnin', and feed the smoke to the leak.

my 2003 Envoy is doing the exact same thing...wants to jump forward when sitting at traffic light and idling is irregular. No ideas???

Change the idle air cont and your probl will be fixed

Had the same problem with my 04 Envoy. I cleaned the throttle body and cured all ills.