Sounds like it could be the Idle Air Control Valve...http://www.2carpros.com/how_does_it_..._iac_works.htm

 

My 2007 H3 has had the same issue that everyone else described. I have talked with numerous people about it and everyone has a different idea of what is causing the problem. Well this weekend I decided to tear into the H3 and take a look for myself.

The solution that fixed it, CLEAN THE THROTTLE BODY BACK TO ITS ORIGINAL ALUMINUM FINISH INSIDE.
Yes that's it, that is all that it took.

Tools required: PH Screw driver, 10MM Socket with extension, carb cleaner and some clean rags.

The inside of my throttle body had a slight brownish/yellow/black grime on the inside. I removed the throttle body and sprayed the inside with carb/throttle body cleaner used a CLEAN rag to remove all of the grime, put it back together and it runs like new.

When I first started the engine it rev'd a little after a short trip down the road the thing ran like new.

It runs like it did the day I bought it. Hope this helps someone else!

 

So here it is. The solution to the mysterious stalling hummers. A lot of people have posted that they all have the same problem, Yea Yea Yea, and yet nobody has posted the solution. Here it is.
Today I took my 2007 H3 with 79000 miles to the dealer for repairs. My H3 stalled all the way into work this morning. I had enough. Turns out that the idler plate was cloogged with carbon. The dealer cleaned the whole fuel injection system for 256.00, now my H3 runs like new. Oh yeah!
Me so happy.
I tried the fuel injector addatives from the auto parts store. I tried running premium fuel. No luck. The dealer used Wynns. Ta da!

 

I had the same problem 2007 with 60,000 miles. Cleaned the throttle body and MAF sensor and it cured everything. 20 minute job

 

I wanta share these two links for the stalling problem, our engine is a lot like the TB's

Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

How to seafoam your 4.2l Gmt-360s - Page 5 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

 

Ummm, I've been around and working on engines since I was 14. What is an "idler plate"? Idler pullys, idler arms, etc but I've never heard of that. Is it connected to the Kenutzien Valve or the Whatcha-macallit-thingyma-jiggy?

 

I have had this very same problem for the last couple of weeks, then a couple of days ago I got the dreaded check engine light and the diagnostic read by Onstar of a misfire code. My 06 Hummer H3 with 75k miles is at the service center as week speak. Come to find it it is one of the 06 H3's that were orginally built with a bad valve seat so know we are told we have cylinder head problems and is going to cost us $3500 to fix. I have been arguing with GM all day since this was a known problem and a complete range of vin #'s were effected by this. GM should be covering this and recall the others who have not had this problem yet. Very frustrating!!

 

Took my '07 w/ 26k miles into the shop today for the issue. Came up with the same misfiring diagnostic code and they told me to take it into the dealer since I still have a powertrain warranty on it...we'll see what happens.

 

Cleaned my MAF and the throttle body but engine still wants to surge when it drops to idle
My engine only does this when it is in open loop and after it warms up and goes to close loop it seems fine. This never really concerned me because it has never stalled, just threatens too.

 

Come on Tainter, every one knows it is bolted directly to the thinga-ma-bob.