Hi Eric, love your YouTube videos, they are the best out there, period.
I own a 2010 GMC Sierra 5.3L Z71 SLT Crew-Cab (LC9 engine) I recently had an event with flashing check engine light and rough running engine. Codes came up P0307 and P0451 (with existing known code P0442). The #7 misfire was my focus and I have done nothing about the evap codes. I swapped coil, plug, wire, and injector with another cylinder with no luck. After research, I suspected collapsed lifter. I pulled the valve cover and found #7 intake rocker loose (I could rock it up and down a 1/4″). I pulled the heads and replaced all AFM lifters (1, 4, 6, 7 – intake & exhaust). Everything else looked good. No wear on lifter rollers, no visible damage to crankshaft. Still #7 misfire. I then replaced oil pressure sensor and the filter underneath, and I replaced the entire VLOM. Still have #7 misfire.
I could really use some advice on how to proceed. I just watched your video on compression testing and I just borrowed a compression tester so I will try that next and provide the results. Anything else I could try?
Thanks in advance,
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