manfredeule4

Siena engine knocking sound

I'm having a strange issue with my 2000 Fiat Siena, gasoline engine, about 90k km on it. Lately, I've noticed a knocking sound, especially when accelerating. The engine also seems to have lost power, and it jerks when I try to speed up. Plus, there's some smoke coming out when I put my foot down. I plugged in an OBD2 scanner, and there's an error code stored, but I haven't had time to properly investigate it. Could it be cylinder heads or pre-ignition? Perhaps an ignition timing issue, wrong fuel octane, or even piston slap? Any ideas?

A 2000 Fiat Siena owner reported a knocking sound, loss of power, jerking during acceleration, and smoke emission. Potential causes considered included cylinder head issues, pre-ignition, ignition timing problems, incorrect fuel octane, or piston slap. Another person suggested carbon buildup in the combustion chamber as a possible cause, which was confirmed by a mechanic. Cleaning the combustion chamber resolved the issue, restoring the vehicle's performance.

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4 comment(s)

Sounds rough! I had something similar happen with my Siena. Same symptoms - reduced power, jerking, and even some smoke. Did you check for deposits in the combustion chamber? That was my problem.

Deposits, huh? Interesting. How did you figure that out, and what exactly does 'deposits in the combustion chamber' mean? Is that like carbon buildup? What did you do to fix it?

Yeah, carbon buildup, exactly! I didn't figure it out myself, to be honest. My mechanic diagnosed it. He said it was causing pre-ignition, which is basically the fuel igniting too early. I would suggest going to the workshop.

Thanks for the advice! I took it to my mechanic, and you were spot on – it was deposits in the combustion chamber. They cleaned it out, and now it's running like new. Cost me 425€, but worth it to have my Siena back in good shape.

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FIAT

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SIENA