Looking for some guidance with a weird misfire in a '99 GMC Sierra K1500 5.7L. I've got a P0300, but no cylinder specific codes.
At idle while in Park cylinder 1 has an occasional misfire. When I put it in Drive and still idling cylinder 2 starts misfiring pretty heavily and 1 still has the miss once in a while. Finally, when under load the heavy misfire moves entirely from 2 to 3.
Once in a while I'll get a P0130 for an O2 sensor that's becoming more frequent. I'm going to change both upstream sensors.
New plugs, wires, cap, rotor and coil, but the problem persists. At this point I'm out of ideas.
At idle while in Park cylinder 1 has an occasional misfire. When I put it in Drive and still idling cylinder 2 starts misfiring pretty heavily and 1 still has the miss once in a while. Finally, when under load the heavy misfire moves entirely from 2 to 3.
Once in a while I'll get a P0130 for an O2 sensor that's becoming more frequent. I'm going to change both upstream sensors.
New plugs, wires, cap, rotor and coil, but the problem persists. At this point I'm out of ideas.
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