HBenn
Mercedes GLC Hybrid Engine Knocking Resolved
Summary of the thread
A 2020 Mercedes GLC hybrid experienced engine knocking, reduced power, jerking during acceleration, and smoke at around 20,000 km, with a diagnostic scan showing an error. The issue was suspected to be caused by carbon deposits in the combustion chamber leading to pre-ignition or detonation. It was advised to check knock sensor readings and avoid prolonged operation to prevent engine damage. After consulting a technician and cleaning the combustion chamber, the engine ran smoothly, and the error was resolved.
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4 comment(s)
HBenn (community.author)
Thanks for the response. I haven't checked the knock sensor readings. Could you explain how to access and interpret that data?
gabriel_moon51
You'll need an OBD-II scanner to read live engine parameters. Look for 'knock retard' or 'ignition timing correction' for each cylinder. Retard values over a few degrees mean the ECU is compensating for knock. Given your symptoms, I advise against prolonged operation. Driving with detonation can cause engine damage. A technician should inspect the cylinder heads and combustion chambers for carbon buildup. Consider professional cleaning. Take it to a workshop immediately. Driving it like this makes it worse.
HBenn (community.author)
I appreciate the advice. I consulted a technician, and it was carbon deposits in the combustion chamber causing pre-ignition. After cleaning, the engine runs smoothly, and the error is gone.
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MERCEDES
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GLC
gabriel_moon51
I had similar issues with my petrol GLC. Knocking, jerking, loss of power. It sounds like pre-ignition or detonation, potentially from carbon deposits creating hotspots. Have you checked your knock sensor readings? If the ECU is pulling timing, that explains the power loss. Ignoring this can damage your cylinder heads.