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2003 2500hd 6.0 not so random misfire
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Question
Will03
I know this topic has been beat to death, and I've read every thread on it and still haven't found my problem. Truck is a 2003 2500hd 6.0 with 265,000 miles. Only throws the code at 2000-2500 rpms and isn't noticeable. Misfires only happen on cylinders 2&3 (P0300) and no other codes are thrown. Fuel trims stay +/- 5% short term and stay right around 6% long term with no change when the misfires start. Both upstream 02 sensors have voltage movement as expected. I have swapped plugs, wires, coil packs, injectors (also checked resistance and all were 10.2-10.5), swapped a known good MAF from another truck, had a crank variation relearn done, compression on both cylinders is 148/150 (cylinder 1 was checked for reference and it was 150 also), replaced intake manifold gasket, and haven't found a vacuum leak. fuel pressure is 55psi running with key off and 50-51 running. i have checked fuel pressure regulator and it is working. I have checked the coil and injector wiring to the main harness and looks good up to there. Checked cats with a vacuum gauge and they are not clogged. I'm not sure where to look next. The only correlation between the 2 cylinders I can think of is that they are companion cylinders in the firing order, which would point to a crank sensor (in my mind), but I am told if a cam or crank sensor fails it would be more of a sporadic misfire and wouldn't only affect 2 cylinders. my next plan is to pull the motor and get the oil pan off to check the reluctor (would really prefer to just swap out a lower mileage motor if I'm already pulling it, but I don't want this problem to follow to another motor). Any and all input is greats appreciated.
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