I have a 2006 H3 that has no codes present and no check engine light on. As long as it is cold it runs fine but after it warms up it will go dead when you let off gas pedal. So any time you let off gas pedal to push brake pedal it goes dead. It will crank right back up and run as long as you keep your foot on the gas. Has anyone had this problem or have an idea on what I can try?

 

Sounds fuel related. I had a similar issue. Start by cleaning your MAF and throttle body.

 

I did that yesterday, no difference.

 

throttle position sensor?

 

I suspect your IAC is not working. Check it by idling the engine and then turn the AIR and headlights on to load the engine and reduce RPM. Does the engine slow then pickup to the original RPM to counter the load? If it does then the IAC is working as thats its job.
If the engine slows...and does not speed up then suspect that the IAC is not compensating. Check it out.

 

I had another vehicle(not Hummer) years ago that exhibited this behavior and it turned out the safety switch that
detects if the motor is running or not was tripped on throttle down. A flap on the intake would come up when air was being drawn
in. This released a switch that controlled power to the fuel pump. If the engine stopped and air quit being sucked in, the flap
would return to closed tripping the fuel pump switch and killing the fuel pump.

The symptom was approaching a stop and releasing the gas. Engine would die and then immediately start when turning the key.
The problem was fixed by bending the contact on the switch so that the flap didn't trip the switch when releasing the throttle. Fixed
the problem.

I have no idea how the Hummer engine is configured, but I would look for this 'safety' switch that turns off the fuel pump
when releasing the throttle.

Good luck....

 

Have you replaced battery connections?
Have you cleaned ground wire connection points at block, chassis and frame? I mean remove degrease, sand, wire brush and reinstall and lube.
Have you recently replaced any parts that may have led to this?
Have you put non oem spark plugs in?
Have you verified that there are no stored codes?