Ive got an 08 Chevy Silverado 1500 LTZ with a 5.3. I was driving on the highway when I had a lifter collapse. Started running rough due to a misfire. Limped her home and determined it was a lifter due to the ticking sound and the misfire. I started digging into the motor. After removing the heads and valve cover. I pulled the lifters and sure enough the AFM lifter on cylinder 6 had collapsed on me. I replaced all the lifters on the passenger side since i had everything pulled already. When I got it all back together I still had a misfire. I changed the fuel injector, coil, plug and wire to help eliminate possible issues. Nothing fixed the misfire on cyl 6. I then took off the valve cover to see the rocker arm wasnt moving. I took it off to inspect the parts and saw nothing. Arm looks pretty good and the push rod doesnt seem bent at all. I put it back together and it ran great. Proceeded to drive for the day and ran perfectly. The next day I make it a mile down the road and the misfire started again. Took the cover off again and the same thing. I believe its the rocker arm for the intake thats not moving (3rd rocker arm from the rear of the engine). I took them off and reinstalled them again. Same situation. Ran great for a day then next day drove it for a mile and misfire again. I will say that the last time I took the rocker arm and push rod off. I had someone turning the engine by hand while I put a little pressure on the rod. There seems to be a sweet spot to where the rod wants to move and where it doesnt. Maybe after driving for a while the rod shifts somehow? This shouldnt be possible though should it? Its suppose to sit on the top of the lifter and I torgued all arms to 22 ft lbs. Any ideas? A few notes: I looked at the cam lobes and didnt see any scaring or pitting, All torque specs were followed. I am no mechanic but I feel like I knew enough to tackle this issue.

 

Did you replace the Valve Lifter Oil Manifold (VLOM)? That should be replaced any time an AFM system is taken apart

 

I did not. Ill be digging into it again here soon and Ill make sure I replace that as well.