Cylinder 5 misfire - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 06-29-2019, 02:23 PM
Bmoroneymd Bmoroneymd is offline
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2007 GMC Envoy SLT
Midnight Blue Metallic 4.2L I6 4X4
Join Date: Jul 2017
Location: Silver spring, md
Posts: 5
Cylinder 5 misfire

Changed coil and plug. Same result. Swapped #4 with #5. Same cylinder 5 misfire. MIL light flashing so definitely seems raw fuel warning me to stop so I don’t burn up the cat. Looking for wiring pin out between PCM plug and #5 coil plug to ring out wires and see if an open or short. Any other ideas from members who feel some other obvious cause besides either PCM itself or broken/shorted wire I’m all ears. Broke down at autozone where it simply detects the coil and plug in that cylinder. Will read actual codes when car gets home. Anyone know the pins to check continuity between?
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  #2  
Old 06-29-2019, 11:22 PM
EnvoyBoy2004's Avatar
EnvoyBoy2004 EnvoyBoy2004 is offline
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2004 GMC Envoy SLT
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Could also be loss of compression on that cylinder or a faulty injector.
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Old 06-30-2019, 07:43 AM
Bmoroneymd Bmoroneymd is offline
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2007 GMC Envoy SLT
Midnight Blue Metallic 4.2L I6 4X4
Join Date: Jul 2017
Location: Silver spring, md
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Yeah briefly thought of those as well. Hoping for broken wire.
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  #4  
Old 07-03-2019, 09:17 PM
Bmoroneymd Bmoroneymd is offline
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2007 GMC Envoy SLT
Midnight Blue Metallic 4.2L I6 4X4
Join Date: Jul 2017
Location: Silver spring, md
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Broken valve spring on intake valve. Valve stayed in place so going to attempt to change them all out and hope for the best
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Old 07-11-2019, 11:03 AM
Denny62 Denny62 is offline
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2008 Chevy TrailBlazer LT
Liquid Silver Metallic 4.2L I6 4X4
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Quote:
Originally Posted by Bmoroneymd View Post
Broken valve spring on intake valve. Valve stayed in place so going to attempt to change them all out and hope for the best
Glad you found it. I haven't had that on a 4.2 but a trick we used to do to change a broken or weak spring was to pull the plug and feed a couple of feet of cotton clothesline down into the cylinder, then roll the crank until things tighten up. It always held the valve in place nicely so we could fix things. My luck it would be stuck but good till I messed with it and even if it couldn't fall completely down it would still make getting the new spring on a PITA. I'd put new keepers and all the rest on it while you're at it, cheap insurance.
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