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Compression Test

RS3 ROCKS May 3, 2019

  1. RS3 ROCKS

    RS3 ROCKS steve

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    Hi ASN. I've carried out a compression test on my 2001 AMK S3 today as fault diagnosis. Does anyone have access to autodata to see what the compression figures should be?

    My car has a Jabba sport stage 2 remap otherwise standard engine and turbo.Figures obtained were as follows:

    Cylinder 1 - 125psi
    Cylinder 2 - 110psi
    Cylinder3 - 125psi
    Cylinder 4 - 135psi

    Mileage is 105k

    I had a stutter and juddering when at 5k revs. After lots of test driving labouring the car from low revs straight into 5th gear I had a flashing EML light and a fault code for cylinder 2 misfire. Following this I've changed the spark plugs and cylinder 2 coilpack. It's smoother but i'm convinced it's still a little judery but it may just be in my head. The cars poly bushed so is rattly when driving anyway.

    Thanks for any advice
     
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  3. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow... Staff Member Moderator

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    Sorry to say they should be more than that... at least 170psi

    <tuffty/>
     
  4. RS3 ROCKS

    RS3 ROCKS steve

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    Going by that they are all very low then. What does this mean ideally? Valve stem seals shot?
     
  5. RS3 ROCKS

    RS3 ROCKS steve

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    I read an article online that gave me hope:

    A compression test reveals the condition of your engine's valves, its valve seats, and piston rings and whether these parts are wearing evenly. Healthy engines should have compression over 100 psi per cylinder, with no more than 10 percent variation between the highest and lowest readings.
     
  6. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    wont be stem seals causing low comp
    pistons/rings/bore and possible poor sealing valves

    next is cylinder leak down test
     
  7. RS3 ROCKS

    RS3 ROCKS steve

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    Thanks Bill and Tuffty for the advice. I'm trying to do the diagnosis myself but I'm at a standstill now. I understand the theory behind the leak down test but don;t have the kit.
     
  8. Tj 0785

    Tj 0785 Registered User Bronze Supporter Silver Supporter VCDS Map User

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    Get a garage to do it think I paid £70 for compression test and leak down test
     
  9. hharry100

    hharry100 Registered User

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    Had an injector go on me once, which also gave hesitation and misfire in one cylinder, worth swapping injectors to see if fault moves to another cylinder.
     
    RS3 ROCKS likes this.
  10. EngineersRus

    EngineersRus Registered User

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    What compression tester are u using? Only because once a used a brand new sealey one and was getting low readings then tried a snap on one and my readings were 170 to 175 so you could try another compression tester just in case. If i remember rightly auto data said compression should be around 170 psi
     

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