I bought a 2005 3.2 Cayenne with full history 55k last September as a private sale/purchase so no comebacks for seller.
Drove it home & by time i had got home, it was running a slight noise/rattle. Next time I started it, it was running rough as you could imagine. I called AA & fault codes galore, misfire on every cylinder.
A brake servo pipe had burst & it was air/fuel ratios had played havoc with running. Got it back from garage & slight rattle was present, this was down to the timing belt tensioner. Tensioner was replaced, engine serviced, plugs replaced & a new coil pack put on. The car ran a treat for a while.
Recently, it started to run rough again, it started a couple of months back & I had put it down to damp cold weather. It would run lumpy on tick-over & even stall when manoeuvring in car parks on occasion. Then as you drove off it would seemingly be fine. At the next traffic lights, it could be perfectly sweet or lumpy as ****.
I started to run Shells top fuel, didn't help really.
The rough tick-over just used to be on odd occasion but now it seems to be the vast majority of the time. Having pulled up at my very well trusted local garage, he instantly said it's popping & it must be drawing in air which is messing with the fuel air ratios & causing rough running. They booked it in, checked it over, plugged it in & drove it down the road to another local garage. Both lots of diagnostics had shown misfire readings on every cylinder.
My garage could not find an air leak & did not have a solution. There was no charge for their service.
Today it runs as sweet as it could. Next time I start it, it could be rough. Motorway journeys seem to calm it down after a run at a steady 70. If I accelerate hard, this will cause it to be rough at next lights.
Please please has anybody seen similar symptoms. I cannot spending at the local Porsche dealership, it's going to bankrupt me & I fear the problem recurring.