SLCHOE
ASE Master Certified + (L1)
Need the codes!
Bad bad bad BAD misfire!
- Thread starter oldsman003
- Start date
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OP
OP
oldsman003
Member
Codes won't do any good considering battery had been dead and cannot drive it to receive any code other than misfire. I had the passenger head off seats and valves look fantastic. No vacuum leaks whatsoever all valve train is spotless and everything seems to operate how it should. I turned engine over with head off and all looked great. Did compression test on every cylinder and every cylinder read over 120psi
SLCHOE
ASE Master Certified + (L1)
I you have 120 psi on every cylinder, you can eliminate flat cam, damaged drivetrain components or timing components.
If you have spark at all 8 cylinders and it is a good strong and consistant spark, I'd say you have a fuel delivery issue on that bank of cylinders.
Did you check for injector pulse on all 8 cylinders?
OP
OP
oldsman003
Member
When I had the head off to check valves per request of my mechanic, I turned engine over to push antifreeze out of cylinders and all injectors were spraying a very nice pattern I noticed because I didn't pull the plenum only un bolted and left everything in tact. So injectors are spraying and coils are good but are not getting power. Harness looks good no breaks or bare spots
SLCHOE
ASE Master Certified + (L1)
There is something amiss here. For your engine to run like that, you either have a compression, fuel or spark issue. That's it. Maybe it is intermittent and you took your readings while things were good? I'm at a loss here. Something is wrong and it has to be n one of those 3 if not a combination but not none of them. I'd re-run the tests myself. Doesn't add up.
Duramax05blk
Full Access Member
i had a similar issue with an 03 lq4. Cats were one cause but you already removed them. Could it be a tuning issue due to not by-passing 02 sensors??? There is also fuel pressure regulator on the drivers side vertical rail approx in middle of rail, This caused me a slight miss fire cant recall what cylinders and a noticeable loss of power. Have you checked the schrader valve for good fuel flow? these trucks are notorious for fuel pumps. Could be limited fuel but not dead yet.
OP
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oldsman003
Member
As I stated my fuel pressure is a solid 61psi at the rails. And my miss isn't a miss any longer it is half the engine. Entirely on bank 2 passenger side. Good spark good fuel good compression all moving internal parts are freely moving no slack at all in timing chain. Proven pcm replacement security relearn.
The o2 sensors couldn't be causing the ridiculous poor rubbing condition with the pcm. I understand it wouldon't run efficiently and for sure wouldn't cause it to run only on 4 cylinders.
This truck will not even back itself or of my drive way right now.
The o2 sensors couldn't be causing the ridiculous poor rubbing condition with the pcm. I understand it wouldon't run efficiently and for sure wouldn't cause it to run only on 4 cylinders.
This truck will not even back itself or of my drive way right now.
OP
OP
oldsman003
Member
Still at a lose here, the only thing I have not changed its the knock sensors. Would a bad one cause this problem?
ccapehartusarmyINF.(ret)
Full Access Member
was this a typo because if the coils are good but getting power you would not be getting any spark
OP
OP
oldsman003
Member
Typo sorry truck has been sitting eveything works everything gets spark air and fuel. But timing is so out of wack it's not firing on bank 2. I just now put it bavk together from being pissed off at it. I apologize for getting the facts wrong. Timing is issue hentz why I'm wondering about knock sensors since one controls each bank. Wondering if having a bad one could cause the entire bank to crap out.
I apologize once again for stating my problem incorrectly
I apologize once again for stating my problem incorrectly
