Rev ups & Dying - Tahoe Hybrid

dcrockss

My 2008 is experiencing an engine rev up at stop lights or when idle. Up to 4000 or 5000 rpms. This is sporadic.
Additionally I am having the engine quite when at stop position and the engine shuts off to "hybrid" when I accelerate the engine quits when gas takes over. I then need to put the car in Park, turn off and restart then it starts and runs. This is particularly bad as it happens only occasionally such as when you are turning left into oncoming traffic or a stop light. I first went to a non affiliated mechanic then to a GM dealer whom I paid $900 to only to have the check engine light go on at the first traffic light encountered. The GM dealer had there "Hybrid Tech service the vehicle."
I don't want to take it back and spend frivolously on bad service that won't accomplish the task of fixing the issue.

gonn60secnz

I own a 08 Tahoe Hybrid with the same problem. I've taken the vehicle in to dealer and they said they have never heard of such an issue, but they can drive the vehicle around until the problem can be replicated then possibly diagnosed at a $130/hr. The issue is difficult to duplicate

spensational

I am having the same issue with my 2008 Tahoe Hybrid, ie, at stop light instead of going into hybrid mode, it rev's up to 4000+ RPM, and at times, will stall when starting from a stopped position, almost like it is stuck between electric and gas modes. Has anyone diagnosed this issue at this point?

thecardoc3

The odds are seriously against anyone having dealt with a problem like this here. Most full time techs haven't done anything with these, there just aren't enough of them out there. The first step however would be to pull codes from all of the modules on the car and prioritize them. The second step would be to experience the symptom and find out by analyzing live data if the high idle is being commanded by the computer as in is it trying to compensate for something or if the high idle is the result of the computer losing control of the TAC (throttle actuator control system). Additional steps that need to be taken would be TSB searches, and check for flash updates and make sure that the vehicle software is fully up to date.

From this point, the next step would be very dependent on what the discovery phase of the diagnostics above revealed. Until proven otherwise, don't let the fact that this is a hybrid vehicle be misleading. Study and analyze the basic gas engine and its throttle controls first just like any other vehicle. Then investigate the hybrid system if necessary.