Help needed please. I recently pulled the drivers side head off (1,3,5,7) to fix exhaust manifold threads. when I put everything back together and now I get a
random misfire flashing MIL. The crazy thing is that the individual cylinder misfire current and history show it on cylinder 4, And I didn't touch that head.
Truck is a 2008 GMC sierra 1500 4.8 LY2. small cam, intake, headers, Exhaust.
The misfire only occurs when:
-Under load-full throttle
-RPMs are between 4500-5500
-truck is in 2nd or 3rd gear. DOES NOT happen in first
Troubleshooting measures I've done so far include:
-Crank Relearn multiple times
-Multiple new AC DELCO plugs gapped at .40
-Different wires
-Swapped individual coil packs and entire set
-Swapped around individual injectors, and all 4 from one side to the other
-New intake manifold gaskets, and torqued manifold in proper sequence
-Checked for any noticeable vacuum leaks
-Compression test on all cylinders. All were in spec.
I'm at a loss. current tune and last log below
17-03-14 08-48-00.hpl
AJ 3-11-17-1.hpt