Turbo hesitation / vibration

[pcskier]

I am searching for any solutions to a hesitation/vibration that has developed on my 03 turbo under hard acceleration or with acceleration on steep grades. It seems as though the hesitation develops once the boost needle is between 0.4-0.8 bar. Once it occurs the boost gauge will drop to its mid position and stay there and the top end acceleration will markedly drop off. When it occurs the car seems to stutter and a vibration is felt through the car, almost as though the transmission is slipping although this would not explain the drop in turbo boost when it occurs. It is very noticeable when pulling a trailer up steep grades.

Since it first developed 3 months ago I have had it in the shop 4 times, each time they have been unable to fix the problem since no warning lights or messages have ever appeared. Last visit they changed all plugs wondering if one was misfiring. The problem has gotten progressively worse and I am wondering if anyone else has had this happen and if is so, how was it corrected.

Again mine is an 03 Cayenne turbo with 32,000 miles

[geza]

Has anyone checked the position of the fuel pick up in the tank/fuel baffle position? Sounds like the momentum of fuel in the tank moving away from the pick up could be causing some starvation...............or a check valve function in the pump/lines may not be working as designed. Downstream issue could also be a fuel filter problem. A final check would be water build up in the fuel tank - being heavier than fuel it spends its time at the bottom of the tank.

Edited November 1, 2005 by geza

[pcskier]

Has anyone checked the position of the fuel pick up in the tank/fuel baffle position? Sounds like the momentum of fuel in the tank moving away from the pick up could be causing some starvation...............or a check valve function in the pump/lines may not be working as designed. Downstream issue could also be a fuel filter problem. A final check would be water build up in the fuel tank - being heavier than fuel it spends its time at the bottom of the tank.

Thanks for your tips. Finally, my service department diagnosed and fixed the problem. It turned out to be a few defective ignition coils which were causing the engine to misfire. I guess as the problem worsened, an error was recorded by the onboard computer.