siegfriedkoehler40
A Klasse engine issues Knocking combustion and deposits
Summary of the thread
A 2019 Mercedes A Klasse with a gasoline engine is experiencing knocking combustion, reduced power, jerking during acceleration, and smoke, with an error code stored. The core problem is suspected to be pre-ignition caused by deposits in the combustion chamber. After taking the car to a workshop, it was confirmed that deposits were indeed the issue, and cleaning them resolved the problem, improving the vehicle's performance.
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4 comment(s)
siegfriedkoehler40 (community.author)
I'm using the recommended fuel. Could deposits really cause engine knock this badly? Is there any chance it's piston slap or something worse with the cylinder heads?
richardherrmann40
Honestly, I'm not sure about piston slap. Deposits are a strong possibility. If it's knocking badly and you're seeing smoke, I'd get it checked by a workshop soon. It could save you money in the long run.
siegfriedkoehler40 (community.author)
Thanks. I took it to the shop, and you were right. Deposits in the combustion chamber. They cleaned it out, total cost 425€. It runs much better now.
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MERCEDES
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AKLASSE
richardherrmann40
That sounds familiar. I also have an A Klasse. I experienced something similar. Have you checked the fuel octane?