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Showing results for tags 'Code P0306'.
Hello, I have a 2000 GMC Sierra 1500 5.3Liter with 246,000 miles. I have a code P0306 for misfire Cylinder #6. I have changed the spark plugs and wires. Then did a compression test and cylinder #6 had low compression at 120psi. All other cylinders had between 180-190psi. Did a leak down test and heard air flowing through the oil filler spout when #6 was at TDC on the compression stroke. Removed the head, valves looked good. When I cranked the engine by hand, the piston for cylinder 6 would not go up all the way to be flush with the top of the cylinder like the other pistons were, it would come up to 1/8” before the top, the go back down. What causes this and how can I fix it? Do I have to replace the piston? Or?? Thank you for taking the time to read this, any input would be greatly appreciated.