I've had a problem for the last 2 years with 4 trips into the local Audi dealer and they've been yet to find the problem. I've not yet read a description that matches my problem exactly on any forum so I'll try to explain it the best I can. The car is a 2008 Audi A4 Quattro 2.0T.

At about 30-40 mph with very little pressure on the gas either on a straight away or a slight incline when the car is low on the gear (a low RPM) I feel a rough spot about once a second pulling the car back slightly. The tachometer will show this movement going up and down by around 200 RPMs or so, again about once per second. It's not horribly noticeable under normal driving and in all honesty, if it weren't for the fact that my warranty is expiring in November, I'd probably just live with it but I feel like it's the beginning of the end of something... not sure what.

I don't know much about the repairs but this all started when I started seeing oil on the top of the engine around the fill hole over a year ago. The repair at that time was a leak from the valve cover gasket (stage 3 oil leak?). They replaced this but just after I had to take it back for a check engine: P0299. They found the turbo bypass valve to be faulty and replaced it.

Since then, as I said, I've had it in a few times for this issue and they've replaced the Crankcase breather and hose, did full computer resets, an update they mentioned for the computer that was available and finally the last time they replaced the flap motor.

It all seems like this could stem from compression/vacuum issues somewhere in the system. I've read various things about the compression buildup in the system that resulted in my turbo bypass valve to go and the valve cover gasket, all of which perhaps had some residual impact on something else? Any help would be appreciated as I believe the dealer is out of ideas. I now live about 500 miles from the dealer (moved recently) and although I need to travel there for work, it's not all that convenient so I'm really hoping to give them some good suggestions on Tuesday when I bring it in.

Thanks in advance!!