2003 Chevrolet Cavalier Repair Question
If the noise is coming from the top of the engine, it could be a collapsed lifter, bad cam (will cause a misfire), or excessive carbon build up on the piston / valves. If the noise is from the lower part of the engine, it could be a rod or main bearing. Remove a spark plug and check it to see if there is a lot of carbon on it. If there is, they make products to eliminate carbon from the intake and combustion chamber. That would be the cheapest first thing to try. Other than that, you need to start taking things apart to check the problem.
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