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Q: Engine misfire cylinder 3

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I'm having a misfire coming from cylinder 3. Replaced coil and plug. Tested compression coming back at around 105 every other cylinder is 125+

My car has 110000 miles.
My car has an automatic transmission.

The misfire could very possibly be from low compression. You want the compression across all cylinders to be within 10% of each other at most. The compression for number 3 is under that threshold. It could be caused by worn or cracked piston rings, damage to the cylinder walls, or possibly from misadjusted or damaged valves.

I suggest you verify the valve adjustments to make sure that the valves are correct. You may also want to find someone that has a borescope to inspect the cylinder walls and pistons for damage.

If you’d like some assistance with a more in-depth diagnosis of your misfire, consider YourMechanic, as a one of our mobile exerts can come to your home to service the car. Best of luck.

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