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Okay guys I bought this truck from a dealership in September. It was used and I got a 30 Day warranty. After the 30 day period, this is what’s happening. I got in my truck and noticed a rough idle. My truck would shake and out of no where the check engine light starts flashing and my traction control light comes on. I took it to my buddies and we got a P0308 Misfire Detected Cylinder 8. So I did some research.. I also had a code which was P219B. Air/fuel mixture ratio. I changed the spark plugs.. didn’t work. I moved coil packs.. the misfire didn’t move. So we watched Live data on the scanner and injector 7 was acting up. So we replaced all the injectors on that side and this truck is still missing.. I’ve ran seafoam through it and cleaned the throttle body and MAS. My buddy things I have a valve issue or something wrong with the cylinder… there is no AFM deleted or anything of that sort. The truck has worked flawlessly until now. 135,000 miles on it. The rocker arms all looked great. please someone give me something to try. I just want my truck fixed lol. posting a link below of what it’s doing…
I have an 05 4.8L Sierra with 293k miles. The last few weeks my truck has had a bit of a rough idle but runs fine other than that. Then my engine light flashed a few times which was P0308. I don't have a scanner that shows missfire count but i can say that in the last two weeks of driving back and forth to work 8 miles both ways, the CEL has only flashed once for P0308. I have swapped coils, wires, plugs, and injectors and it made no difference. I've sprayed carb cleaner around the intake with no change in idle/sound. After fighting with a compression gauge with damaged threads and dropping a plug on the concrete, ground strap down, i finally got to test compression today but the engine was cold and i only tested one side. Dry tests: Cyl 8: 140 Cyl 6: 195 Cyl 4: 190 Cyl 2: 215 Cylinder 8 wet test came out at 215. Fuel pressure with key on was 50, running at idle: 58. With all that said, this truck burns around half a quart of oil between oil changes (5k intervals) The compression test seems pretty conclusive that the rings are bad in cylinder 8. Should I give up and accept the fact that this engine is just about done or could there be something else causing the missfire?