Compression test results and questions
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    FST Noob! Droski727's Avatar
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    Compression test results and questions

    I bought a used focus ST with 45k miles. I had a compression test done and they read 145 145 140 145 in order of cylinders left to right. Do you think this is cause for concern? Any things to check? I know they are close together but under the 160-170 of a new engine. The mechanic that did the test did not hold the gas pedal down because he said it wouldn't make a difference because it's drive by wire. Would this matter? Also, I'm in Florida so basically sea level. It was 90 degrees outside if that makes a difference.

    This is my daily and I want to make sure it lasts me a few years without major issues. I don't plan on driving it too crazy, just like the occasional back road.

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    FST Senior Member BizKhalifa's Avatar
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    Things that need to be done to get an accurate reading:

    • Engine needs to be warmed up to have proper ring sealing
    • All 4 spark plugs need to be removed
    • Install compression tester on one cylinder
    • Hold down the gas and clutch so that the injectors do not fire
    • Press the ignition button, wait about 15 crank cycles, then press it again to stop

    Those are the proper step to get an accurate reading. If he failed to follow that, then just do it yourself. Super easy to do.

 

 

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