A4 Rough Start & Poor MPG: TPS/Valve Issues Alert

Had a similar issue with my 2011 A4 1.8 TFSI last year. With some experience working on cars, I recognized these symptoms immediately as they mirrored what I went through. The unstable engine idle and poor fuel efficiency were exactly what I experienced. The throttle response was getting worse gradually, making the car feel sluggish and unpredictable. After running diagnostics, it turned out to be a defective accelerator pedal module. The repair involved replacing the entire pedal module assembly. Total cost was 205 Euro including parts and labor. The throttle cleaning was also done as preventive maintenance while they had everything apart. The difference after the repair was night and day, stable idle, proper throttle response, and fuel efficiency went back to normal. To better assist with your specific case, could you share: Any warning lights on the dashboard? When did you last have throttle valve maintenance? Does the issue happen more when the engine is cold or warm? Have you noticed any unusual sounds when pressing the accelerator? These details would help determine if your issue is similar to what I experienced or if it might be something else.

Last service was actually at 165000km, about 2 months ago. The check engine light came on yesterday, and the engine idle gets notably worse when the car is fully warmed up. No unusual sounds from the accelerator, but there is a slight hesitation when pressing it. The throttle valve has never been serviced as far as I know. When I checked with a scanner, I got error code P2015 which points to the intake manifold. Definitely going to have the throttle body checked and cleaned as part of diagnosing this.

Thanks for those details, this actually sounds quite different from my pedal module issue, especially with that P2015 code showing up. Based on my experience with these engines, the symptoms you describe combined with that error code strongly suggest an intake manifold runner control issue, not just a dirty throttle valve like I initially thought. When my throttle position sensor went bad, I never got that specific code. The unstable engine idle and poor fuel efficiency in your case are classic signs of a failing intake manifold, the control valve gets stuck, affecting air distribution through the engine. I had my intake manifold replaced at 180000km due to similar symptoms, though I was getting a different error code. The repair cost was around 450 Euro including labor. The engine throttle response improved immediately after replacement. Since your throttle valve has never been serviced, I would still recommend having it cleaned, but focus first on getting the intake manifold checked. The hesitation you mentioned when pressing the accelerator is very typical of intake manifold runner issues rather than a throttle problem. Quick question: Does the engine idle get rougher specifically when you turn on the AC or other electrical accessories? This could help confirm if its definitely the manifold.

Thanks for all the feedback. Yes, the idle does get noticeably worse when the AC is running. After reading your responses, I am more convinced its the intake manifold causing these issues rather than just the throttle position sensor or control valve I initially suspected. Going to book it in next week to have both the air intake system and throttle cleaned, plus have them do a proper diagnosis of the manifold. The engine throttle response issues and rough idle are getting worse, so better to address it soon before it leads to other problems. Really helpful to hear about your similar experience with the manifold replacement. The 450 Euro cost seems reasonable considering the work involved. Will update once I get it looked at and know exactly what needs replacing.