car engine ramblings- low compression symptoms

  1. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    got a fuel injected car , idles bad with popping down the exhaust

    runs good above idle or with a pig rich mixture , starts fine , no excessive blow by out the filler cap , no misfires or randomness above idle

    does this sound like i should invest in a compression tester?
     
  2. johnik

    johnik Member

    Messages:
    339
    Location:
    sunny Somerset
    testers are cheap enough so why not ?, sounds like an exhaust valve is leaking
     
  3. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    if it was leaking...why no issues above idle or with a rich mixture?
     
  4. voipio Member

    Messages:
    505
    Cambridge, UK
    Was the timing belt changed recently? It could be bad timing, though a leaking exhaust valve would have more impact at low engine speeds since it would be not- quite-shut for longer at low revs.
     
  5. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    timing belt is all good
     
  6. johnik

    johnik Member

    Messages:
    339
    Location:
    sunny Somerset
    Stevo, i had the same on a SAAB, turned out to be a burnt exhaust valve.... do a compression test before you start buying parts.
     
  7. p0689109 Member

    Messages:
    1,450
    Location:
    stoke on trent,england
    What car or engine is it?
     
  8. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    its an old polo 3f engine code , basic ye olde fuel inj without much diagnostic options

    seems to fit the symptoms of air leak which i can find none or a leaky valve

    would i be best getting a comp tester or leak down tester? just thinking could it be ring issues or doesnt that match the
    symptoms
     
  9. Wallace

    Wallace Member

    Messages:
    5,511
    Location:
    Staines, Middlesex, England.
    I would start with a compression test and if within 10% of each other look at the injector pintles. How are you richening the mixture?
     
  10. colnerov

    colnerov Member

    Messages:
    2,698
    Location:
    Nr Gatwick UK
    Hi, Do a compression test, that will tell you whether its rings or valves.

    Colin
     
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  11. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    injectors have been sent away and tested /cleaned okay

    will get a tester and see what happens
     
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  12. dobbslc

    dobbslc Forum Supporter

    Messages:
    3,173
    Location:
    Hertfordshire UK
    Valve clearances?
     
  13. Ruffian Member

    Messages:
    878
    Location:
    Devon UK
    Burnt exhaust valve.
    Cylinder leak off test would probably be better but a compression test would be a starting point.
     
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  14. steveo3002 Member

    Messages:
    4,380
    cambridge uk
    hydraulic self adjusting

    any thoughts why super rich (9% co) makes it smooth?
     
  15. Ruffian Member

    Messages:
    878
    Location:
    Devon UK
    Map sensor.
     
  16. fordman Member

    Messages:
    42
    Fife, Scotland
    Lambda sensor?
     
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  17. steveo3002 Member

    Messages:
    4,380
    cambridge uk
     
  18. slim_boy_fat

    slim_boy_fat Forum Supporter

    Timing?
     
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