OP
OP
Marbor
Member
I agree and was thinking the same. I couldn’t get cy1 on the pic but there are no misfires on 1-2 at all I’m guessing to pull the OP and go from there
08 suburban LTZ 5.3 misfire at idle
- Thread starter Marbor
- Start date
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iamdub
Full Access Member
I'd try a steeper slope than 15° to 100% confirm the O-ring thing.
Yea, I would think something like 30 degrees would do it. Hard to find that sometimes. May have to elevate the back, a bunch, to simulate.
OP
OP
Marbor
Member
I’m more after the pump I think it’s a mfg defect.
iamdub
Full Access Member
The pressure release valve has been known to get stuck open. I think the story I recall seeing was an aluminum shaving left behind from machining wedged the piston in the bore at the open position so it was always bleeding off the pressurized oil. RPM above idle was enough to overcome the "leak" and provide sufficient pressure.
If you go so far as to replace the pump, you may as well delete AFM using known quality parts and be done with it.
OP
OP
Marbor
Member
Hello all it’s been awhile but still chasing the same issue, rig has been pretty much parked hogging up parking.
Any how I’m still having the oil pump pressure issue but believe I somehow figured out the misfiring on cyl 7.
So basic diag shows FT are in the -10 B1 and -8.8/-9 B2 then I get the misfire counts and shaking. Once rev over 1200 rpm FT normalize and misfires go away so pcm is taking fuel away which is causing the mis. I unplug the B2 crank vent and leave open FT crash +20s which is pretty much dumping fuel but the mis count drops to 0 with a few here and there. No bad idle car is solid drives fine with tons of power but I’m sure it’s not a permanent fix. Once plugged in FT are back in the -9 -10 and misfire start to count up.
What can take fuel away? things I looked at 02s are working as should MAF is good injectors swapped out with known good ones, coils plugs, wires all good. injector leak down test performed air filter replaced. I want to get this misfire fixed before I dig out this oil pump once the weather breaks and I have a few days over 35 deg.
Any how I’m still having the oil pump pressure issue but believe I somehow figured out the misfiring on cyl 7.
So basic diag shows FT are in the -10 B1 and -8.8/-9 B2 then I get the misfire counts and shaking. Once rev over 1200 rpm FT normalize and misfires go away so pcm is taking fuel away which is causing the mis. I unplug the B2 crank vent and leave open FT crash +20s which is pretty much dumping fuel but the mis count drops to 0 with a few here and there. No bad idle car is solid drives fine with tons of power but I’m sure it’s not a permanent fix. Once plugged in FT are back in the -9 -10 and misfire start to count up.
What can take fuel away? things I looked at 02s are working as should MAF is good injectors swapped out with known good ones, coils plugs, wires all good. injector leak down test performed air filter replaced. I want to get this misfire fixed before I dig out this oil pump once the weather breaks and I have a few days over 35 deg.
Last edited:
OP
OP
Marbor
Member
Hello this is my final post just when I thought I was starting to WIN.
So long story short misfire on 7 was pretty much fixed rig was driving great no flashing CEL idle smooth and felt good still had the low oil pressure and seen a video on the tube similar situation and the guy changed oil and used ACDelco filter, I had a K&N. So I did an engine flush dumped the oil replaced with with 5/30 FS and oem Delco filter, behold OP was at 60psi at CS and steady at about 35-38psi warm at idle and while driving would bump up to just under 60-57 psi. So great I fixed it and was so happy drove to work no issue perfect drive my rig is back yeah!!!
FML this morning taking my kid to school I noticed AFM kicking in between 4-8 randomly then everything went to hell lifter collapse misfires trans codes and just tapping like no tomorrow. So here I back at ground zero SMH…..
So long story short misfire on 7 was pretty much fixed rig was driving great no flashing CEL idle smooth and felt good still had the low oil pressure and seen a video on the tube similar situation and the guy changed oil and used ACDelco filter, I had a K&N. So I did an engine flush dumped the oil replaced with with 5/30 FS and oem Delco filter, behold OP was at 60psi at CS and steady at about 35-38psi warm at idle and while driving would bump up to just under 60-57 psi. So great I fixed it and was so happy drove to work no issue perfect drive my rig is back yeah!!!
FML this morning taking my kid to school I noticed AFM kicking in between 4-8 randomly then everything went to hell lifter collapse misfires trans codes and just tapping like no tomorrow. So here I back at ground zero SMH…..
Tahoe14
Full Access Member
That sucks!!!
OP
OP
Marbor
Member
Well had to dig in since I was pretty bored and all honey do list have been completed.
Pulled the head and low and behold. May slap together with known good lifters. I have the original ones from bank one that were not an issue prior to rebuilding. Worst case I make till spring fingers crossed and this will buy me time to find a replacement motor and have it deleted.
Pulled the head and low and behold. May slap together with known good lifters. I have the original ones from bank one that were not an issue prior to rebuilding. Worst case I make till spring fingers crossed and this will buy me time to find a replacement motor and have it deleted.
Attachments
OP
OP
Marbor
Member
Last and happy update. On this thread and a learning curb.
After rebuilding bank 1 lifters with OEM still had the misfire on bank 1 all cylinders and FT were crazy -16–20%
Went ahead and rebuilt bank 2 with OEM lifters and while at it replaced the oil pump with Melling 365 and green O ring. 1st start after completed was amazing. No ticks OP just over 60psi once at operating temp idle OP is just below 40psi I’ll take it. Rig is super quiet now and all misfires FTs are normal. I’m so glad I finally got this figured out.
Also the power is awesome. Now I’m gonna look at getting one of those DOD disablers in hopes for saving the lifters from collapsing in the future.
Lesson learned use only OEM parts and never try the cheap route.
After rebuilding bank 1 lifters with OEM still had the misfire on bank 1 all cylinders and FT were crazy -16–20%
Went ahead and rebuilt bank 2 with OEM lifters and while at it replaced the oil pump with Melling 365 and green O ring. 1st start after completed was amazing. No ticks OP just over 60psi once at operating temp idle OP is just below 40psi I’ll take it. Rig is super quiet now and all misfires FTs are normal. I’m so glad I finally got this figured out.
Also the power is awesome. Now I’m gonna look at getting one of those DOD disablers in hopes for saving the lifters from collapsing in the future.
Lesson learned use only OEM parts and never try the cheap route.
