My son and I bought a 2002 Camaro, 3.8L with 130k Miles for him to work on and learn. Nice condition overall and got it cheap. It came with the check engine light, and we knew it had a cylinder missfire by the P0301 code. Thought it would be an easy fix with a tune up.

Changed Spark Plugs, wires and coil packs... No help.
Swapped fuel injector from another cylinder and misfire code didn't change.
Did a compression test wet and dry.. 150 in all cylinders except 1, it was at 120.
Bought one of those kits you stick on the radiator with the liquid to see if it's a head gasket leak. Fluid didn't change colors.
Did a "cigar" smoke test through the brake vacuum line to look for vacuum leaks and didn't see any smoke leaking out.. but not sure how good of a test this is versus using a smoke machine.

Is there anything we should do or check before pulling the valve cover and checking the valves?

 

is there a large amount of blow by when you take the oil fill cap off while running? could still be head gasket, also stuck ro bent valve, broken piston ring. all I can think of.

 

Good idea to check blow by at the cap..Thanks Since the compression didn't change from wet to dry test, and I put a camera in the cylinder to check ring, I figured that would have ruled out piston ring. But blow by cap test is quick and easy to confirm..

 

I guess a few more things are possible. failing lifter, broken valve spring or flat cam lobe. so not holes in piston or other things look wrong using camera?