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Cylinder Misfire Issue on 2008 Sierra 4.8L

This is a discussion on Cylinder Misfire Issue on 2008 Sierra 4.8L within the Performance forums, part of the General Discussion category; I have a 2008 GMC Sierra with the 4.8L. Last August give or take I swapped the plugs out with ...

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    Registered User guessohw's Avatar
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    Cylinder Misfire Issue on 2008 Sierra 4.8L


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    I have a 2008 GMC Sierra with the 4.8L. Last August give or take I swapped the plugs out with the E3 plugs and the truck ran fine. A few months later when in Arizona the truck stated to stutter off and on at random then threw a check engine light "multiple cylinder misfire" which I was able to clear using my Edge Evolution unit. Shortly after I swapped the plugs again hoping it was just a plug and the problem seemed to go away. My parents currently have the truck in Arkansas since I am deployed and they said it did it again a few weeks back so they took it to the GM dealership and they swapped the plugs again this time with factory plugs. Two days ago my parents say they truck started doing it again and threw another check engine light. Any thoughts on what this could be? I am taking the edge unit of this week when I come home on leave and will be installing the BlackBear AutoCal unit but I want to make sure its not something serious like a damn stripped spark plug thread or something. Also the driver side back plug by the firewall seemed to have exhaust blow by or something when I swapped it and I believe the dealership said the same thing. Each time all plugs where tightened down the same. I believe this is the trouble cylinder. Thanks

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    Registered User guessohw's Avatar
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    Re: Cylinder Misfire Issue on 2008 Sierra 4.8L

    Also what heads would be able to swap onto the truck (4.8L) in case it was a head issue? If I do heads I'm gonna swap the cam too so just thought I would ask.

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    Re: Cylinder Misfire Issue on 2008 Sierra 4.8L

    A single bad plug will not cause the Random/Multiple misfire problem. You have a problem global to the entire ignition system, or another system such as fuel delivery. Your pump could be starting to fail causing intermittent problems. On the ignition side, likely candidates are Crank sensor, Cam sensor, knock sensors. Also - what are you running for an air filter? A fouled up MAF could be causing issues also.

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    Registered User guessohw's Avatar
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    Re: Cylinder Misfire Issue on 2008 Sierra 4.8L

    Im running the complete K&N Air intake system. My MAF did get water on it back when we had a big flood if that might be something. You can look at the screen mesh inside the tube and see almost like a white line or something across it. I never really thought anything of it.

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    Re: Cylinder Misfire Issue on 2008 Sierra 4.8L

    At the very least, take the MAF apart and clean it. Use CRC MAF cleaner, nothing else.

 

 

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