I have a 2002 Toyota Corolla (1zz-fe engine with 236k miles on it) and did a compression test on a warm engine. My readings are:

150 - 150 - 140 - 175

I've read that the difference should not be more than 15%. I am more in the 20% range. Any suggestions?

Note: I changed my piston rings a few months ago.

Thank you!

1 Answer 1


When you changed the piston rings you did check the bores for ovality and scoring and honed them so the new rings would seal properly. Or did you just fit new rings...

That may explain the difference you see now. To reduce the difference then you need to do the bores properly...

Of course the difference might also be the valves not sealing correctly - which you need to check.

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