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Q: Problem with number five cylinder.

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I am having a problem with the number five piston cylinder. The piston rings may be damaged. I had a combustion test performed and the readings on this cylinder were low. The car engine is shaking and rattling violently.

A: If you have low compression on a cylinder, ...

If you have low compression on a cylinder, you can determine whether the problem is with the top or bottom of the engine with a wet compression test. This test involves squirting a little oil into the cylinder; if the compression reading improves with the oil the problem is likely worn rings, a worn piston, or a worn cylinder wall. If it does not improve, suspect a problem with the valve train. A certified technician from YourMechanic will be able to inspect your vehicle for you.

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