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S40 knocking combustion smoke

My 2000 Volvo S40 with a gasoline engine is acting up. It's got this crazy knocking combustion thing going on, especially when I accelerate. I'm losing power and it feels like the car is jerking. Plus, there's smoke! And of course, the error memory isn't empty. Anyone seen this before? Could it be the knock sensor?

A 2000 Volvo S40 was experiencing knocking during acceleration, power loss, jerking, and dark smoke emissions. These symptoms suggested incomplete combustion, possibly due to deposits in the combustion chamber. A suggestion was made to check the cylinder heads for deposits, which typically requires professional tools and expertise. After taking the car to a workshop, it was confirmed that combustion chamber deposits were the issue, and cleaning them resolved the knocking and smoke problems.

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4 comment(s)

I had a similar issue with my S40 a while back. Reduced engine power and jerking are definitely not good signs. Is the smoke dark or light? Also, have you noticed any changes in your fuel consumption? It might be worthwhile to check the cylinder heads for deposits.

The smoke is kind of dark-ish. Fuel consumption seems normal, haven't really paid much attention to it though. What kind of deposits are we talking about? And how would I check for them? I'm no gearhead, just trying to figure this out.

Dark smoke often indicates incomplete combustion, which supports the deposit theory. Unfortunately, checking the cylinder heads properly usually requires specialized tools and knowledge. Given the knocking and smoke, continuing to drive it could cause further damage. I would recommend taking it to a qualified workshop for diagnosis. If it's indeed deposits in the combustion chamber, cleaning it could be the answer.

Thanks for the advice! Took it to the shop, and you were right – combustion chamber deposits. Cost me 425€ to clean, but the knocking and smoke are gone, and the error's cleared. Feels like a new car!

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VOLVO

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S40