2006 Suburban loss of power

[nodog]

I've carried my 2006 Suburban (123,000 miles) to three shops and one dealer now to avail. The engine stumbles when accelerating and struggles going up even small hills or bridges and struggles to accelerate. I'm $1600 into this and still have the same problem. I have replaced all 8 coil packs, plugs, wires, upstream and downstream O2 sensors, catalytic converters, Throttle Position Sensor, accomplished compression test (approx 190 lbs on all cylinders), fuel pressure test, dealer cleaned intake, dealer cleaned fuel injection and rails. The private shops kept the truck for three weeks and after not pinpointing the problem advised me to carry it to a dealer. They charged me nothing for labor and discounted the price of the parts. The dealer kept the truck for four days and came up with something different each day. Wanted to charge me nearly six hundred dollars but settled for $260. Dealer advised tearing down the top end (makes no sense as compression is good and holds for over five minutes) for $800 and then another $2000 to reassemble if no problem found. Is this something anyone else has gone through? I use the Suburban to tow a camper but there is no way it has the power to pull itself much less a trailer. I hate to say it but I beginning to lean towards buying a Toyota Tundra if I don't find a solution to this problem soon. I really like my Suburban but I can't afford to throw more money at guessing what the problem is.

[nodog]

So I made about a 350 mile trip this weekend with the Suburban. It started off feeling like it should then about fifteen miles in power was gone. Even the slightest increase in road grade would result in the truck kicking into overdrive and high rpms. Fuel mileage is only 13.7 at speeds between 60 to 70 mph for most of the trip.

If anyone has any ideas at all of what could be causing this please post. Is it even possible to contact GM for possible causes or will they just throw out the standard check the Tech Bulletins?

[Doug_Scott]

When they replaced the convertors was it because they had broken up inside the convertor shell? If so, then you may want to drop the exhaust after the convertors and take it for a long drive. The muffler may have pieces of the convertors honeycomb inside it, and they may roll around blocking exhaust flow randomly. I would also get the shop to stick a temporary turn down pipe on the now open exhaust to prevent and damage to floor pan when running on highway trying to reproduce the issue. The exhaust may be a tad loud, but the convertors will do a bit of "sound shaping" making it not real loud.

[88m53453]

live stream while driving , watching timing and fuel trim etc will give the answer

[Jsdirt]

Need someone that specializes in drivability issues on these OBD-II vehicles. Sounds like the shops you went to were all parts changers, and not troubleshooters, unfortunately. One bad wire, or a bad connection could cause all of this. The computer could be bad. Someone who knows what they're doing needs to troubleshoot this.

[Jay P]

If turning the traction control on/off changes the engine power without spinning the wheels then something is telling the ECM to pull power. Like someone else mentioned you need to data log to find the problem. Do you know anyone with EFILive or HPTuners (record while driving). They would be able to data log for you.

 

Jay

[nodog]

LOL! It probably would have been somewhat useful if the dealer (Rick Hendricks Chevy Dealer in Norfolk) would have been parts changers. It was their written report that prompted me to swap the coil packs around and resulted in the discovery of four bad coil packs. I don't know why they didn't see that in their own printout.

Today I changed out the MAF. I thought I may have stumbled on the problem on the way to the auto parts store when I cut the Traction Control off. I was surprised when the vehicle felt like it had life in it. Then on the way back I cut the Traction Control back on and the power still felt right. I went home and changed the MAF out, that's when I found out the dealer hadn't touched the intake at all as it was filthy all the way through the intake plenum. I drove the truck several times today and it did fine until this evening then lost power again. After cutting off the traction control again it was better but not up to full power. I really like this truck, it's a Z71 and has four captains chairs in it making it really comfortable.