08SILVERADO1500

I know, that's my last option is to pull the head. Though I do know how to do it as I've done a stuck lifter on the same side before. I believe it was in #5 but I'm not sure. A lifter definitely does not seem to be the case. I just want to find the cause. The repair is not a problem. I don't know if I have a vacuum gauge for the application. I know I have some but they are old units like 80's era mist likely.

That does make sense, however mine feels like a continuous misfire as if it is a fully stuck lifter. It's not a hit and miss situation. But I'll still try this and see what happens. Pretty simple option to try with only a few bolts.

Asilverblazer I did check compression but I feel the gauge is way old and does not register correctly. So I feel that test is inconclusive. Especially, that it showed low compression and then removing the gauge thumps very loud from the spark plug port.

They move when I had the valve cover off and rotated the motor over by hand. I had the coil pack rail off so I didn't want to start the motor.

Update: valve cover off, all rocker arms move especially the 2 on cyl #7

Also quick question, has anyone EVER had the missfire issue, and done nothing except get the afm delte programmer and had the issue resolve itself?

Ok, just pulled the plug and started the engine. Plenty of spark and sounds like a whole lotta compression. I've still gotta find my gauge to check the compression. Idk if I have stated before, i had a major missfire one time and could hear the ticking lifter and i believe it was on the same cylinder. I did yank the head and replace the bad lifter. Now it seems that maybe this has happened again. Same cylinder, brand new lifter. But I hear no rattle as to say I've got a stuck lifter. Thanks y'all for the input, I guess it's just time to pull the valve cover and see.

Ahhhhhh gotcha. Makes sense. Ok so the voltage to the coil pack should be same as voltage from the battery? Thanks for y'all's help.

CamGTP What do you think I could find under the valve cover? Also, if I pull the wire to the coil pack, what voltage do I need to be getting to the coil?

Does have AFM not sure it's working anymore. Has used oil lately. Also had every bolt loose on the valley pan when I did the intake manifold gaskets a while back. Which caused a major oil leak I thought the rear main seal so I pulled the tranny back and replaced it before I found the problem. Should I just try the AFM control delete module?

Ok ya'll, I'll try to keep it short. I have an 08 1500 5.3 over 300k miles was a well maintained work truck. Had stuck lifter a while back pulled head replaced ran fine. Ran for a long time with a exhaust leak on driver side @ the Y pipe to the manifold. I think it burnt out the sensors for running so long that way. replaced y pipe I got a rough idle and then CAT started rattling. new cats new 02's. swapped coil packs, wires, plugs and injectors, added some torque to the intake manifold . just have not check compression yet but will tomorrow. Please help!!!