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Lost Cylinder Compression

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by DeathSammich, Apr 7, 2018.

  1. DeathSammich

    DeathSammich Member

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    Have a recent rebuilt l67 and lost compression in 2 cylinders. Both around 60psi. I have new heads to put on it but was just wondering, if 2 cylinders are down on compression would that cause a major increase in fuel consumption? Like 16-18l per 100 average? Thanks
     
  2. delcowizzid

    delcowizzid on holiday

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    Are they 2 cylinders side by side
     
  3. EYY

    EYY Well-Known Member

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    2 bad cylinders will definitely give increased fuel consumption
     
  4. DeathSammich

    DeathSammich Member

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    Passenger side 140, 75, 60
     
    Last edited: Apr 8, 2018
  5. DeathSammich

    DeathSammich Member

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    Like a really big hit in consumption or only a little?
     
  6. delcowizzid

    delcowizzid on holiday

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    Looks like you'e blown the head gasket between those 2 cylinders
     
  7. DeathSammich

    DeathSammich Member

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    Nah engine has been rebuilt twice. Mechanic said rings but it was clearly the head. Its probably warped or cracked. I got another set to put on.

    Do you reckon the low cylinders would cause a major bump on fuel consumption?
     

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  8. delcowizzid

    delcowizzid on holiday

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    Well it' running on 4 cylinders so yeah fuel consumption through the roof lol.normally when 2 side by side both lose compression its the gasket blowing between the 2 cylinders cracked heads won't lose compression like that .valves not closing would or smashed rings do a leak down test plug compressed air into one of the low comp cylinders with the rockers undone you'l soon find where the airs going it will be gushing out either into the crankcase from rings out the exhaust or intake if its valves out the cylinder next doors plug hole if it' the gasket or bubble out the Radiator if its cracked the head or blown the gasket to water
     
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  9. immortality

    immortality Moderator Staff Member

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    Classic blow head gasket between the cylinders numbers.

    It's going to be a head off job regardless.

    edit: find a new mechanic...
     
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  10. delcowizzid

    delcowizzid on holiday

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    Probably damaged the gasket a little when you had the l36 Injectors in it by accident and boost has finished it off over time
     
  11. DeathSammich

    DeathSammich Member

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    Is there anyway to post video? I have a few videos of the vacuum gauge at cold start and shifting through park and reverse
     
  12. delcowizzid

    delcowizzid on holiday

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    Put them on YouTube and post links on here
     
  13. DeathSammich

    DeathSammich Member

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  14. DeathSammich

    DeathSammich Member

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    I posted them, what do you make of them?
     
  15. delcowizzid

    delcowizzid on holiday

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    Not a lot needle might be swaying a little gauge is probably to slow reacting to see bad fluctuations especially with a hose all the way into the cabin on top a proper diagnostic vacuum gauge will see a lot more
     
  16. DeathSammich

    DeathSammich Member

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    Well on a cold start the vacuum drops really low and the engine rumbles before vacuum picks back up. It idles smooth in park but crap in gear
     
  17. immortality

    immortality Moderator Staff Member

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    That could be a tune thing.
     
  18. delcowizzid

    delcowizzid on holiday

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    It's lost a third of its idle torque with 2 cylinders out and if it has blown the gasket its eroding the block and heads at the point of the leak more and more the longer it runs
     
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  19. immortality

    immortality Moderator Staff Member

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    Delco is right. No matter what the gauge shows, you are down 2 cylinders so it's time to rip that head off and fix the problem.
     
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  20. DeathSammich

    DeathSammich Member

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    Alright I'll take the rocker covers and wind it over to see if they all lift the same. If they do I'll take the heads off and fit these others on. If it's still got low comp then god knows. Cracked block it is
     

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