2008 Tahoe Hybrid with 82k miles. Has been driving normal with no problems. All service is up to date. Weather has been normal. 60-80 degrees Fahrenheit

I was stopped at a light and the engine slowly revved up on its own to 5k rpm and then back down. It went back down to 500-1k rpm and was idling sporadically between 600-800 rpm.

When starting to move from that same light, I pressed the gas like i normally do, but then it revved up to 1500 RPM like it "slipped" and then finally engaged and started to move. Drove ok back to work.

Went to leave work later that day, Started fine but still noticed the "slipping" effect when starting to move from a complete stop.

Got to the bank on the way home and parked. Went to leave the bank and put it in reverse, pressed the gas, rpms went up and no movement. Put it back into "P" and restarted the Tahoe. Did the same thing again. Again, shut it off and back on.

Once more it did not move when in reverse until i pressed the gas a little harder and jolted back very abruptly. It jolted hard in reverse. It felt like it engaged and disengaged very hard until i was able to get out of the parking spot after a few attempts of pressing the gas a little harder. Drove home and still felt the "slipping" while moving from a complete stop. I checked the trans oil when I got home and it looked and smelled normal.

Heres the kicker... no SEL or any warnings of any kind. I even plugged in my older Bluetooth ELM OBD 2 adapter with the OBD2 app on my phone and no codes were reported as being stored. I have an appointment with the dealer in a few days but with no codes readily available, Im hoping they can replicate the issues and find the cause. Its no longer under warranty either..

Any suggestions? I am not moving the Tahoe until the day I need to take it to the dealer.

Im leaning towards a faulty Dampener Assembly (Torque Converter-like assembly) from the engine revving up that high while in "D" while stopped at the light. Maybe Ill get lucky and its just a faulty control module. Oh boy.

 

Update: The day after this incident I decided not to drive it at all. The following day I started it and drove it around with no problems whatsoever.

I have been driving it since with no problems.

Got the Ho back from the dealership today. No codes stored or anything found to be wrong. All modules are up to date software/firmware-wise.

Must have just been the ghost in the machine. I do need new motor mounts so ill be installing those in the next week.

 

I'd think the Tranny fluid was maybe low.
I had a similar issue where a bolt inside my grand Cherokee 42RE transmission solonoid pack had backed out allowing fluid in a pressured port to escape through the gasket when the fluid was warm. No codes given and it worked fine until the tranny heated up.

 

Thanks for the suggestion. I checked the fluid and it is where it should be as well as the records show that it was changed 6 months ago.

Its been running fine ever since the incident. If there is not codes stored/check engine light the dealer cant do much.

 

Any updates? We have a 2008 with about 150K and it's sporting the same symptoms. Mostly go to take off, engine revs higher than pressure on gas peddle. Truck moves, but feels like it's slipping. Then starts to catch, rpms down to expectation. Ocassionally get herky jerky start or stall. No code. Seems to do this more when hot and driven for a lot of small trips - 2 to 3 miles. Has no bearing if engine is warm. Restart and drive in M4 seems to do the trick.

We've had the engine, transmission and control panel checked by dealer. Cannot reproduce on demand. At this point, it feels like a bad sensor feeding bad information to the computer and thus it can't decide how much of either electric drive or engine drive it needs.

 

I do have an update. I apologize for not having posted it on my original thread.
Here is the link to my comment. https://www.greenhybrid.com/forums/f...09/#post260057

This is what I said, Its not good. Please refer to the context in the thread as I follow up to some of the other comments following my reply.

"I wanted to chime in. My 08 HyHoe was also showing the symptoms of your original post. I had no check engine lights or alerts. The dealer said the Hybrid battery was within tolerance. So i called a local reputable hybrid shop. He connected his computer to the Hoe and in is opinion GM has defined the operating tolerances to give the illusion of long battery life but sacrifices the drive quality the worst the battery gets.

I decided to replace all the cells with a new batch of current gen ones. He ran diagnostics on the cells that were in my Tahoe and they were all around .9Wh. New they are to report 6-7Wh per cell. So they were not bad per-say, just worn and through with their expected life.

So what does GM consider "Within Tolerance"? After installing the new pack, Its a whole new vehicle with no more hesitation or any of the annoying driving issues as before.

I paid 2200 for new cells and labor. I recommend it if you are driving an 08 as it will get worst. I am also having the shop modify the fan speed so as to provide more airflow to the batteries constantly."

 

DirtRunner21,

Many Thanks for the answer. We opted for just replacing the battery so hopefully we can get another 100,000 to 150,000 out of the vehicle.

So... the jerking and stalling was getting to the point that something had to be done. GMC dealer quoted $4,600 for a new battery pack installed. I live in the DFW area and found a shop that specializes in Hybrids (thanks to your suggestion). They quoted $3,300 installed. We're at 165,000 miles and love the truck as well.

Glad I did it. Solved all problems. No stalls, no jerking, no slips.