2008 chev suburban misfire help needed.
Thread Starter
Teching In
Joined: May 2020
Posts: 2
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2008 chev suburban misfire help needed. Hello guys, hope all are staying safe and secure with what we're calling reality these days.
Anyway,
2008 Chevrolet Suburban 5.3L AFM engine. 221xxxkm.
Cylinder 1 big misfire on load.
swapped ignition coil (misfire stayed on 1)
changed ignition wire ( same)
changed with a new spark plug incase (still same)
Now I was wondering about the DOD but the spark plug is drenched in fuel. figuring the intake valve atleast is opening somewhat.
I haven't yet done a compression check, threw my scan tool on it and drove it. misfire is apparent at idle. kind of levels off with slight throttle off a light. scanner still picking up the misfire but feels somewhat smoother.
Also, drove it on the highway to 70mph let off the throttle and misfire is gone under decel but right back under load.
Not sure where to start.
codes are PO300 only cylinder showing big misfire is cylinder 1. cylinder 8 has a slight at idle.
As far as I've read, possibly bent pushrod, not thinking its lifter but possible.
any help would be good
Anyway,
2008 Chevrolet Suburban 5.3L AFM engine. 221xxxkm.
Cylinder 1 big misfire on load.
swapped ignition coil (misfire stayed on 1)
changed ignition wire ( same)
changed with a new spark plug incase (still same)
Now I was wondering about the DOD but the spark plug is drenched in fuel. figuring the intake valve atleast is opening somewhat.
I haven't yet done a compression check, threw my scan tool on it and drove it. misfire is apparent at idle. kind of levels off with slight throttle off a light. scanner still picking up the misfire but feels somewhat smoother.
Also, drove it on the highway to 70mph let off the throttle and misfire is gone under decel but right back under load.
Not sure where to start.
codes are PO300 only cylinder showing big misfire is cylinder 1. cylinder 8 has a slight at idle.
As far as I've read, possibly bent pushrod, not thinking its lifter but possible.
any help would be good
Last edited by 79camaro1; May 1, 2020 at 07:40 PM.
Thread Starter
Teching In
Joined: May 2020
Posts: 2
Likes: 1
Ended up being the cylinder 1 lifter intake lifter. Freed it up. The VLOM is defective forcing the intake valve to collapse. Unplugged the VLOM and ran a diablosport tune through it. Runs as it should now.
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