1. Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;)

random compression readings on one cylinder

Posted by eli96talon, Mar 1, 2012

Please Support JNZ Tuning
Please Support Morrison Fabrication
  1. eli96talon

    eli96talon Proven Member

    Joined Feb 16, 2012
    mt.pleasant, Texas
    I was wondering if anyone can explain why I keep geting strange compression readings on cylinder 3.sometimes its at 90 then at 120 then at 145 then 130.the compression goes up and down any way it wants. Also its not the tester,when i comp. Test the other cylinders they always read 185,184,185 it never changes.can anyone tell me why this is happening?
  2. Twinturbo120

    Twinturbo120 Supporting VIP

    Joined Aug 14, 2010
    Miami, Florida
    Have you tried doing a "wet" compression test to see what happens?

    Street Build 506  1

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
  3. bryanwheat

    bryanwheat DSM Wiseman

    Joined Aug 16, 2004
    Columbia, Missouri
    You probably have a bunch or carbon on the valves and combustion chambers. When the reading is low there is likely a piece of carbon between the seat and valve, when it burns out the compression goes higher. Either that or you have a junk compression tester.
  4. spic21

    spic21 Proven Member

    Joined May 14, 2010
    albany, Louisiana
    if this is the case try so sea foam, ive seen it work miracles with build ups.
  5. BogusSVO

    BogusSVO Proven Member

    Joined Jul 1, 2009
    Pensacola, Florida
    Run a leak down test.

    You may have an excessivly worn guide in the head that allows the valve to seat at a cocked angle
  6. eli96talon

    eli96talon Proven Member

    Joined Feb 16, 2012
    mt.pleasant, Texas
    The head is 2 weeks old all the componants are new,the headgasket is also new..there is no carbon build up on the valves.I also did a wet test to see if the compression would go up and it didn't.its just strange on day the compression is low and misfiring then 2 hours later its high,then low,then high.
  7. iugrad92turbo

    iugrad92turbo Supporting Member

    Joined May 22, 2007
    Kalamazoo, Michigan
    Sounds like something is still wrong, maybe there was a problem with the guides in the head, i learned never to assume things. Head may be fairly new but, you could have a problem in there, regardless.

    7K  5

    1992 Eagle Talon TSi
    awd · manual · 1G DSM
  8. eli96talon

    eli96talon Proven Member

    Joined Feb 16, 2012
    mt.pleasant, Texas
    Im puting in am order to s.I.m for a fresh block since I don't have any trust in this motor.also I have issues that when under boost the #3 piston pushes the spark plug gap closed shut

Share This Page

Support Vendors who Support the DSM Community
ECM Tuning ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications OHM Racing RixRacing RockAuto SouthBay Fuel Injectors STM Tuned Track Decals Track Sculptures VR Speed Factory