I have had a real hard time figuring this one out and am hoping someone from here can give me more insight into what may be happening.
Here's the backstory: 2013 Silverado with 5.3 came in with cylinder 7 misfire. After several tests it was determined there was something wrong with the valve train and the lifters were replaced on that bank. Fast forward to this week. After putting the truck back together it runs nice and smooth until about 9 seconds then it has a dead miss on cylinder 7. If i take a standard compression test it is fine (~180psi). If I do a running compression test the compression drops to 0 in about 9 seconds. Once the compression drops to zero if I immediately turn the engine over the compression returns. The compression never drops while doing a standard compression test no matter how many times I let it crank over. One other aspect that was changed was when the VLOM was off plugs were pressed into the engine AFM towers to essentially delete them. In my opinion I think the cylinder 7 intake valve is staying closed, I need to run it with the valve cover off to test this.
Thanks for the quick reply. I wasn't aware of that. Luckily the plugs are threaded although I am not optimistic in the small thread working to pull them out. One thing I can't explain is why it is only cylinder 7. I suppose it could be other cylinders but the scan tool shows 7 as a dead miss after the 9 seconds. I appreciate the support, I have purchased your lifter release tool and VLOM plug for my avalanche and they worked flawlessly. I orderd the tower plugs off amazon during the holiday break. Turns out that was a mistake...