Mystery P0306. Help Needed

[tex50]

2003 Silverado 1500. 5.3. Getting code P0306. Missing at idle on cyl 5 and 6. Worse when warm. Missing above idle at 6 only. Only occasionally missing on 6 at above 1500 rpm. Compression test 6= 150lbs. 4=180 lbs., 5= 190lbs. Did the following: Major tuneup including wires, plugs, filters etc.. Cleaned throttle body. Cleaned and tested maf. Swapped maf with known good no change. Swapped coils, plugs, wires and injectors to other cylinders. Same code. Replaced cps and performed cps relearn. Checked for bad ground. Pulling the little hair I have left out. Suggestions appreciated. Thanks.

[jrrod2004]

2003 Silverado 1500. 5.3. Getting code P0306. Missing at idle on cyl 5 and 6. Worse when warm. Missing above idle at 6 only. Only occasionally missing on 6 at above 1500 rpm. Compression test 6= 150lbs. 4=180 lbs., 5= 190lbs. Did the following: Major tuneup including wires, plugs, filters etc.. Cleaned throttle body. Cleaned and tested maf. Swapped maf with known good no change. Swapped coils, plugs, wires and injectors to other cylinders. Same code. Replaced cps and performed cps relearn. Checked for bad ground. Pulling the little hair I have left out. Suggestions appreciated. Thanks.

 

 

according to SI, it may be a bad ground on the ground strap itself. Other place would be on the ECM harness....

[98 Z71 SLT]

Flat camshaft lobe

 

Measure valve lift, at rocker arms