T-Roc Performance Issues: Knock Sensor Investigation

I had a similar auto repair situation with my Golf (2020 1.5 TSI) last winter, and having some experience with VAG cars, those symptoms sound familiar. The check engine light and rough idle turned out to be caused by a loose connection in the wiring harness near the knock sensor. The mechanic found that the cable connection had worked itself loose over time, causing erratic sensor readings and affecting the ignition timing. The fix was straightforward, they cleaned the connector, secured it properly, and cleared the error codes. Total cost was 95€ for diagnosis and repair. The engine ran smoothly afterward with normal fuel consumption restored. Before jumping to conclusions about needing a new knock sensor, it would help to know: What engine does your T-Roc have? What year is it? Have you noticed any specific situations when the problems are worse (cold starts, highway speeds, etc)? Have you had the error codes read? Getting this information would help determine if your car problems are similar to what I experienced or if there might be other issues at play.

Thanks for the detailed response. My T-Roc has had its latest service at 30000km and is currently at 33518km. The issues seem most noticeable during cold starts and worsen during highway driving. I have not had the error codes read yet, but will get that done this week to better diagnose the problem. The improved fuel efficiency after your repair sounds promising. My symptoms match yours closely, so I will have the mechanic check the wiring connections around the knock sensor first before replacing any parts.

Great to hear you are getting the error codes checked. After fixing my Golf's wiring issue, I had a similar case where the knock sensor connector needed cleaning at around 35000km. These connectors can accumulate dirt and corrosion, affecting engine performance. Since your symptoms match what I experienced, especially the cold start issues and highway performance problems, having the mechanic inspect the wiring harness and connections is a smart first step. Poor sensor readings can cause the ECU to adjust ignition timing incorrectly, leading to engine knock and increased fuel consumption. When the mechanic fixed my car, they also performed a full diagnostic scan which revealed that the engine management system had switched to a conservative fuel map due to unreliable knock sensor data. This safety feature explains the higher fuel consumption we both experienced. A thorough inspection and cleaning of the sensor connections might be all you need. In my case, once the wiring was secured and the codes were cleared, fuel efficiency returned to normal and the check engine light stayed off. Let us know what the error codes reveal. This will help confirm if your T-Roc is facing the same electrical issues I encountered.

I really appreciate the insights about the knock sensor wiring. After getting the malfunction indicator codes read yesterday, it turns out the diagnosis matches what you experienced. The mechanic found corroded connections affecting the knock sensor readings, which explains the poor fuel efficiency and rough running. The total repair cost was 120€, including cleaning the connections, checking all nearby wiring, and clearing the error codes. The ignition timing is now back to normal parameters according to the scan tool. The engine runs smoothly again, especially during cold starts, and highway driving is much better. The auto repair was simpler than expected, no parts needed replacement, just proper cleaning and securing of connections. My fuel consumption has already improved noticeably on the drive home from the workshop. Thanks for helping me avoid unnecessarily replacing the entire knock sensor assembly.