VW Fox Diesel: Rough Idle & High Fuel Consumption Fix

Had similar issues on a 2009 VW Polo 1.6 TDI. The symptoms matched exactly, high fuel consumption, rough idle, and startup problems. The throttle position sensor was failing, causing incorrect readings to the engine control unit. The air intake system inspection revealed carbon buildup around the throttle valve, severely restricting proper airflow. The control valve assembly needed complete replacement, not just cleaning, as internal wear had developed beyond serviceable condition. This was a serious repair requiring specialized diagnostic equipment. The throttle body electronic components were integrated with the car throttle assembly, making it impossible to replace individual parts. The entire unit needed replacement to restore proper engine management. After fixing the throttle control module, fuel consumption returned to normal, and the engine idle stabilized immediately. These symptoms should not be ignored as they can lead to increased engine wear and potential damage to other components if left unaddressed. Worth noting the air intake system should be inspected first, as carbon deposits can sometimes cause similar symptoms without requiring full component replacement.

Thanks for sharing your experience. That throttle valve issue sounds exactly like what I am experiencing with my Fox. After reading about the carbon buildup affecting fuel efficiency, I am convinced I need to get this checked properly. Could you remember roughly how much you paid for the complete repair? Also, has everything worked fine since the control valve replacement, or have you noticed any other issues? Will definitely have the air intake system inspected first before jumping to full replacements. The car throttle symptoms match perfectly with what you described.

Thanks for asking about the costs. The complete repair came to 205€ for fixing the defective accelerator pedal module, which included replacing the faulty throttle valve. The price covered both parts and labor. Since getting the control valve replaced, the engine has been running perfectly with no issues whatsoever. Fuel efficiency returned to normal levels immediately, and the rough idle completely disappeared. The air intake system now functions as intended, making the engine response much smoother. This repair was money well spent, especially considering how the failing throttle valve was affecting overall engine performance. Regular maintenance of the air intake system since then has helped prevent any recurrence of the carbon buildup issues. One piece of advice: make sure your mechanic properly calibrates the new throttle components after installation. Proper calibration is crucial for optimal engine throttle performance and fuel economy.

Finally got the car checked today. Turns out the throttle body was completely clogged with carbon deposits, just as you mentioned. The mechanic showed me the buildup and it was shocking to see how restricted the airflow had become. Ended up paying 180€ for a thorough throttle cleaning service and sensor calibration. The mechanic also cleaned the air intake system while they were at it. Much cheaper than I expected after seeing your repair costs, and luckily I caught it before needing a full replacement. The difference is incredible. The engine idle is smooth again, starts up instantly, and feels much more responsive. Drove about 50km after the service and can already tell the fuel efficiency has improved significantly. Really glad I asked here before spending money on unnecessary repairs. The accurate diagnosis saved me both time and money. Will definitely keep up with regular maintenance to prevent future buildup.