compression test results... please tell me how it looks...
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This is a discussion on compression test results... please tell me how it looks... within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I did a dry compression test today to diagnosis my misfire issue here they are... and please if anyone knows ...

  1. #1
    Registered User 06scoobyrex's Avatar
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    compression test results... please tell me how it looks...

    I did a dry compression test today to diagnosis my misfire issue here they are... and please if anyone knows the specs please tell me how they compair...

    06 subaru WRX EJ255

    Cylinder #1. 90-120
    cylinder #2. 60-120
    cylinder #3. 80-120
    cylinder #4. 80-110

    I've replaced the spark plug in the 4cy and switched around the coil packs plus the dealer checked the injector too and it all checks out.... any ideas? Next I'm going to check the fuel filter/pump and sock and also going to reground the ground wire on that cylinder's coil pack... if that doesn't clear it up I give up...
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

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  3. #2
    Registered User 06scoobyrex's Avatar
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    Bump.... anyone?
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

  4. #3
    He simply abides. SD_GR's Avatar
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    The numbers seem too uniformly low to be true. You started all this looking for a solution to a misfire in cyl4, yet now all four cyls are relatively low. Did you crank the motor long enough to get an accurate result?
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Registered User 06scoobyrex's Avatar
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    I thought I did, but the engine was cold too... so I'm sure that would make a difference as well... now that I've been reading about it online... had the engine been warm would the numbers be higher or lower?
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

  6. #5
    He simply abides. SD_GR's Avatar
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    In theory I'd expect the numbers to be higher, as one would think things would seal better as metals expand under heat.

    I don't know if you disconnected the fuel pump power supply, or even if the chance presence of fuel in a cyl would affect the numbers much, but the engine temperature would make a difference for sure IMO.

    In any case from what you have said in this and the other post I can't tell whether the compression is your problem with the CEL, but I don't think so, for what that's worth.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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    Registered User 06scoobyrex's Avatar
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    I couldn't find the relay for it, so I took out the back seat and disconnected the clip on it... the main reason I did the test was to see if it was an internal engine issue and since the numbers are within 10% of each other and it was a cold start it should be fine.... if it were a dead cylinder there would've been a big difference in the numbers... so I'm thinking it has to be the ground wire on the 4th cylinder... it is a small misfire and that would make sense for the situation, cause if it would've been one of the other issues that I checked there would be a more noticable cause....
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

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    He simply abides. SD_GR's Avatar
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    I tend to agree with the line of thinking. Regrettably ground faults and misfire CELs seem to be hard to trace sometimes.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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    Registered User mudferret's Avatar
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    Elevation affects your results; SLC...4300 ft... you'll never see sea level numbers. 120 psi at your altitude is not bad.

    It is odd that that 4th cylinder is lower however. Perhaps try doing that one again and get a leak down test. There are compensation factors for various altitudes, idealized, so it's best to go by your local atmospheric pressure if you want a rough idea (not normalized data from the weather channel, you have to find "station pressure").
    ...Rob.
    MMVI WRX - VF43 Airboy Tuned @ 3500'

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    Registered User 06scoobyrex's Avatar
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    Sd- missfires are a major PITA it pinpoint, but I've had pretty easy fixes in the past.... also subaru's are very finicky and the slightest difference somewhere will cause a symptom of some kind...

    Mud- thanks for the info, that makes sense with the elevation would cause lower readings and numbers... I'll have to check the local atmosphere pressure here...

    Thanks guys your are awesome...
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

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