Audi A3 Knock Sensor Troubles Impact Performance

I had a very similar issue with my 2011 Audi A4 2.0T last year. Having some experience with basic car maintenance, I initially thought it might be something more serious when the warning light appeared along with poor performance symptoms. After experiencing the same issues, rough idling and decreased fuel efficiency, I took it to my regular workshop. The diagnostic revealed it was indeed a knock sensor problem, but specifically related to a faulty cable connection to the sensor. These car problems were surprisingly straightforward to fix once properly diagnosed. The repair involved replacing the wiring harness connector for the knock sensor. Total cost was 95 Euro for the complete fix, including labor. The car has been running smoothly since then with no engine knock or warning lights. Before suggesting anything specific for your case, could you share: Have you noticed any specific driving conditions when the warning light appears? Does the rough idle happen more when the engine is cold or warm? Have you scanned for specific error codes? Any recent maintenance work done before these symptoms started? This information would help determine if your issue is identical to what I experienced with my A4.

Thanks everyone. Just got my car back from the last service at 13084km. The mechanic did an ignition timing check and discovered the engine knock was indeed related to a faulty knock sensor, just as suggested. The wiring looked fine but the sensor itself needed replacement. Auto repair costs came to 220 Euro total with parts and labor. Poor performance issues are now completely resolved and the warning light is finally off. The shop also checked the surrounding components while they were at it, everything else looks good.

Thanks for the update on your A3. The higher repair cost makes sense since you needed the full knock sensor replacement, while in my A4 case it was just the wiring connection. The malfunction indicator staying off is a good sign that the repair was done properly. Just did my latest service at 14500km and everything is still running perfectly since my knock sensor wiring fix last year. No warning lights or performance issues. These 2.0T engines are pretty robust once you address sensor issues properly. For anyone else reading this thread who spots similar symptoms, uneven idling, higher fuel consumption, and check engine warnings, definitely get it checked early. Proper diagnosis of knock sensor issues helps prevent any potential engine damage from incorrect timing adjustments. Have you noticed any improvement in fuel efficiency since the repair? My consumption dropped back to normal within about 2 tank fills after the fix.

Important maintenance lesson learned here. The mechanic confirmed the knock sensor was causing the engine problems. Auto repair bill came to 220 Euro with parts and labor, which seems fair considering they had to replace the entire sensor unit. The warning light is now off and performance is back to normal. They did a thorough check of surrounding components during the malfunction indicator diagnosis which helps prevent future issues. Really glad I got this sorted before any serious engine damage could occur from incorrect timing. Worth noting my fuel economy is already showing improvement after just one tank fill. Thanks for helping me diagnose this correctly, saved time at the shop since they knew exactly where to look.