Chris1995

Hey everyone,
I own a 2009 A4 with 6 speed A/T and I have been running into some issues, mainly with highway driving. So the issue is that while coasting on the highway with moderate throttle, the car bucks or surges in 5th or 6th gear and drops in rpm (about 100-150 rpm). Usually this happens between 60mph and up to 80 mph and is worse when on an incline. Car idles fine and at WOT I have noticed similar "bumps" but never as intense as the cruising ones. The car has 96k miles but the engine was just replaced about 4k miles ago (oil consumption issue covered under warranty). But, even before the engine replacement, this surging was a problem. No codes are being thrown and I have checked for pending ones as well. Just changed the fuel filter (which was a pain in the ***) and still no change aside from a little smoother acceleration from stop. Can anybody help me out with this? Could it be a EGR valve, if this car even has one? Thanks in advance!

Horzu

I had the same issue with my 2010. I also had an oil problem and when they did a stage 1 repair they also flashed the CPU(?). That permanently fixed the problem. The flaash was done at around 40,000Km. I am now at 155,000. Also, after new rings were installed the car burns no oil between changes at 7500Km. Happy camper!

Chris1995

I was thinking about upgrading to a stage 1, did you get an APR tune?
Also they tried changing the O-Rings on my engine first but it was still burning through a quart every 300 miles! I bought a lemon engine so they ended up replacing the whole thing

Chris1995

Ignore that about the tune, I misread completely. I'll see if I can get it flashed at the dealer

Horzu

I had stage 1 & 2 done before the pistions. At one test they did do something with the EGR but I really do think it was the flash that fixed it. Depending on cost you may want to try the EGR valve first.

Chris1995

Okay, I looked into the EGR valve before because I figured since my car was burning so much oil before, that thing HAD to be clogged. However, I have no clue where it is on my engine or if it even has one. Do you happen to know where the valve is on the B8? It's not diesel by the way.

Horzu

I have no idea... maybe pass by the dealership?

treilley

I had this exact same symptom with my 2010. It has an APR stage 1 tune and many others have blamed that as the source. Well, shortly after this started happening I started getting P0299 code. I replaced the Turbo and the surging has stopped.

I also have the stage 2 oil consumption fix and after 50k miles still do not add any oil between 5k changes.

Chris1995

I'm thinking it's not the turbo, only because I have heard a blown turbo before and right now it sounds normal. Also I'm getting no codes so I am still stumped...

treilley

My turbo wasn't blown. It was just not producing any boost at lower RPMs because of dreaded loose wastegate linkage. The turbo attempting low RPM boost is what was causing the surging.