Subaru wrx Compression test?
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This is a discussion on Subaru wrx Compression test? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Well, tomorrow I'm going to do a compression test on my stock 14k miles, 04'WRX. I would like to know ...

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    Subaru wrx Compression test?

    Well, tomorrow I'm going to do a compression test on my stock 14k miles, 04'WRX. I would like to know what exactly are the compression reading in psi for a "good engine".



    Thanks in advance.

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    Registered User EvoEatr's Avatar
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    Impreza Manuals | ken-gilbert.com

    Keep in mind that it is important for the cylinders to be close in readings than have one or two off considerably from the others...Any reason for the compression test? Are you chasing a problem?

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    Registered User teflon_jones's Avatar
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    What's considered a good reading varies with mileage. A pretty much new motor should be 150-160 in all cylinders. Well-maintained lower mileage motors can still get these numbers. Motors at 100k will probably be closer to 130ish, but they can go higher or lower.

    You should consider getting a leakdown test while you're at it too.
    Scott
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    Quote Originally Posted by EvoEatr View Post
    Impreza Manuals | ken-gilbert.com

    Keep in mind that it is important for the cylinders to be close in readings than have one or two off considerably from the others...Any reason for the compression test? Are you chasing a problem?
    I need a compression test because I have a misfire P0304, and before buying anything that is expensive I decided to go with the test. BTW should I do it with the car warm/cold??

    Thanks, hopefully I get an answer before 11am (that is when I'm going to test it).

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    Registered User EvoEatr's Avatar
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    So you really only have only 14k miles on the car, and you have a misfire? Check the basics first, plugs, coil packs etc...I have had a few of these develop these codes after many many miles like around 120k 150k, and it turned out that they needed a valve adjustment. However with 14k miles it seems somewhat unlikely unless of course you beat the car like no other, or it was set to tight at the factory...

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    ooo sorry... typo. My car has 145k miles and earlier today I performed the compression test, well only on side (had to go deal with something very important) tomorrow I'll finish the rest.

    So as of now the results of the car, cold engine:

    135, 150,---,---

    The first one probably did it wrong, since for the second one I actually counted down while for the first one I cranked it two times really quick. Was going to retry it again but something came up.

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