VW TDI Rough Running & High Fuel Use, Throttle Issues

I had a similar issue with my 2005 Jetta TDI about 2 years ago. With moderate experience working on diesel engines, I recognized those exact symptoms, poor engine idle, increased fuel consumption, and rough starts. Initially, I thought cleaning the throttle body would solve it, but after inspection, my workshop found the accelerator pedal module was defective, affecting the engine throttle control valve signals. The faulty module was causing incorrect throttle position readings, leading to the fuel efficiency problems. The total repair cost was 205€, including parts and labor. After replacement, the engine idle smoothed out immediately and fuel consumption returned to normal levels. To better assist with your situation, could you provide: Current mileage, Any check engine lights, Whether you notice any delay in throttle response, If the issues started suddenly or developed gradually These details would help determine if your case matches what I experienced. The control valve system in these engines is quite similar across the TDI range from those years.

Thanks for sharing the details. My Golf just had its service last month and is at 139143km. After reading your experience, I checked the throttle response, and there is a notable delay between pressing the pedal and engine response. The air intake and throttle body were actually cleaned during the service, but it did not resolve the issue. The reduced fuel efficiency and rough running started gradually over the past 2-3 months. The check engine light comes on intermittently, usually after longer drives. Based on the similar symptoms you described, I will have the workshop check the accelerator pedal module. The car throttle behavior you mentioned matches my experience exactly.

Thanks for those extra details. The symptoms you describe match my Jetta situation even more closely now. When my pedal module was failing, I also noticed the check engine light would appear after longer trips, especially on highway drives. The gradual onset of problems and the fact that throttle cleaning did not help points strongly toward an electrical rather than mechanical issue. The control valve system relies heavily on accurate signals from the pedal module to maintain proper engine idle and throttle response. Since your recent service did not fix the problem despite cleaning the throttle body, this further supports the likelihood of a faulty pedal module. The intermittent check engine light is another telling sign, mine did the same thing before completely failing. Have the workshop run a diagnostic scan specifically focusing on the throttle position sensor readings. For reference, my repair involved: Module replacement: 150€, Labor: 55€, Diagnostic testing: 35€ The improvement in fuel efficiency alone made the repair cost worthwhile, and the engine idle returned to normal immediately after the fix.

Thanks for all the input. I will definitely get the pedal module checked out. Just scheduled an appointment at the workshop for next week. They quoted around 220€ for the full diagnostic and potential module replacement, which seems in line with what you paid. I tracked my fuel consumption this week and I am using about 30% more diesel than usual, so fixing this issue should pay for itself pretty quickly. The throttle response delay is getting worse, especially during my morning commute when the engine is cold. Even after the throttle body cleaning during my recent service, these problems persisted, so your experience really helps confirm my suspicions about the pedal module. Will post an update after the workshop does their diagnostic and repair. Hopefully the engine idle and fuel efficiency issues will be resolved as quickly as yours were. The symptoms match exactly, right down to the check engine light behavior after longer drives, so I am optimistic this will fix it.