johnnyb8

My 2009 A4 with 95,000 miles has started to exhibit an obnoxious rough acceleration at low RPMs in first and second gear. The problem is most noticeable when the engine is cold.

The following video shows a light/steady first gear acceleration - notice the tach bouncing slightly. It looks subtle but it's very noticeable while driving.

https://*******/IKP4

Spark plugs recently replaced so I can rule that out. Other ideas that first came to mind were cleaning the throttle body or changing transmission fluid. Has anybody else experienced this issue that can lend some advice?

Does the bouncing tach automatically point to an engine-related issue or could this be drivetrain-related?

mecgmecg

Has your timing chain ever been replaced?

johnnyb8

Yes, actually just last week. I just had the Stage 2 oil consumption fix done (new pistons) and had them replace the timing chain and all guides, etc, as well as spark plugs at the same time. This issue was present beforehand though..

mecgmecg

Does the tach bounce if you stay in Park and apply some throttle? Just trying to hone in on whether it's an electrical issue or drivetrain issue.

johnnyb8

It doesn't seem to be noticeable while in neutral.

johnnyb8

i should also mention it's a manual transmission.

Moviela

Could be motor mounts. Engine idles OK in neutral, but seems to run rough when shifted into gear with clutch in.

johnnyb8

No, it's felt when the car is in gear and accelerating at low RPMs. The feeling is much more of a complete shudder or hesitation, not just engine vibration.

The problem seems to be getting worse but I'm very confused as to what it could be. The fact that the engine "accelerates" smoothly in neutral but not when in gear makes me think it's transmission-related, but the fact that it's much more noticeable when the engine is cold seems to contradict that. Any ideas?

Ryan Mills

I'd look to see if there is any carbon buildup on the intake valves and if the intake manifold flaps are clean and working as designed.

johnnyb8

Thanks, Ryan. I was thinking of starting by cleaning the valves, throttle body, and fuel injectors to see if that resolves the issue as it's probably about the cheapest first step I could take.