Mercedes CLA Hybrid Engine Knocking and Smoke

I also have a CLA, although I don't have the hybrid engine I had a similar issue a while back with knocking and reduced power It turned out to be pre-ignition due to carbon deposits Pre-ignition is when the fuel-air mixture ignites before the spark plug fires, causing that knocking sound The knock sensor is there to detect this and adjust the timing to prevent damage, but it sounds like it's not fully compensating in your case Have they checked the injectors Dirty injectors can cause poor fuel atomization, leading to more deposits

Injectors, huh I haven't considered that When you had the issue, were the symptoms exactly the same Jerking and smoke too What exactly did you have to do to fix it Was it just cleaning, or did they need to replace stuff

Yeah, the jerking and smoke were present, especially under acceleration Although pre-ignition can be caused by a number of issues, I believe your mechanic is correct about carbon deposits It's fairly common, especially in direct injection engines In my case, they performed a combustion chamber cleaning service But given your mileage and the severity of the symptoms, it's probably best to get a professional diagnosis and let them decide the best course of action This could be a larger problem

Thanks a lot for the advice I took it to the workshop, and they confirmed it was indeed carbon deposits They did a cleaning, and the car runs perfectly again I did not know about pre-ignition, that makes a lot of sense Hopefully, it will last for a while Again, thank you