VW Beetle Rough Idle + High Fuel Use Points to Bad Sensor

Had similar symptoms on a 2011 VW Golf with the 2.0 TSI engine. The check engine light and rough idle initially pointed to a knock sensor, but the actual issue was a loose wiring harness connector at the sensor. This caused incorrect ignition timing and increased fuel consumption. The main signs matched yours, unstable idle, poor fuel efficiency, and erratic engine performance. The loose connection made the ECU receive inconsistent signals, causing it to run rich as a protective measure. The fix involved properly securing the wiring connector and cleaning the sensor contacts. This was not a major repair, but leaving it unfixed could have led to serious engine damage over time since incorrect knock detection can affect engine timing. Best practice is to get the specific error codes read first. While knock sensor issues are common on these engines, the symptoms can also indicate other problems like ignition coil failure or vacuum leaks. Starting with proper diagnostics helps avoid unnecessary parts replacement.

Thanks for confirming the wiring harness issue. That aligns with what my mechanic said about electrical connections often being overlooked. My malfunction indicator light actually cleared after fixing the sensor wiring, and fuel efficiency went back to normal. Do you remember roughly what the total repair cost was? Also curious if you had any similar warning light problems since getting it fixed? My VW Beetle has been running smoothly after the repair but want to make sure this is a long term solution rather than just a temporary fix.

After getting the knock sensor connection repaired on my VW Golf, I paid 95€ for the complete fix. The mechanic found the main issue was a poor connection at the sensor plug that needed cleaning and proper securing. No more malfunction indicator lights since the repair was done a year ago. The engine knock detection system works perfectly now, no warning lights or poor performance issues have returned. The original symptoms like high fuel consumption and rough idle completely disappeared after the wiring was properly secured. This type of repair typically provides a lasting solution since incorrect ignition timing caused by faulty knock sensor signals was the root cause. Once the electrical connection is properly restored, the system can accurately detect and adjust for engine knock again. Just make sure to keep the engine bay reasonably clean to prevent future connection issues. The repair should be a permanent fix as long as the wiring harness stays properly connected.

I finally got my car fixed last week and wanted to share my experience. The auto repair shop found the knock sensor wiring harness was indeed the culprit, just like others mentioned. The repair cost was surprisingly reasonable at 120€, much less than I expected for a VW. The malfunction indicator light disappeared right after they cleaned and secured the connection properly. My fuel efficiency is back to normal levels and the engine runs smoothly without any unstable idle. The mechanic showed me how the loose connection was causing the ECU to misread engine knock signals. After one week of driving, no warning lights have returned. The engine performance feels solid and consistent. Much better experience than my previous repair attempts. Thanks everyone for helping identify the real issue instead of jumping straight to sensor replacement.