My 2007 Chevy Tahoe 5.3L has check engine light on. Pulled codes and getting P0304 (cylinder 4 misfire). Swapped coils from cylinder 2 to cylinder 4. Swapped wires from cylinder 4 to cylinder 2. both of those produced no changes. Still misfiring on 4. I also did a compression test and am posting the results below. Below is some data that I pulled from the OBD port also. Any ideas? My thought is to check the injector for blockage -any thoughts? from the data collected it appears to be misfiring on more than just cylinder 4 but not throwing codes for the other cylinders. Should I replace the spark plugs they have been in there for a while. current spark plugs have been in there for 30,000 miles. would appreciate some help. just some background: back in 2017 had both cylinder heads rebuilt as I was getting misfiring on cylinder 3 and mechanic tested compression and determined some exhaust valves were leaking/burnt. It ran fine since then until recently.

back of engine
8- 195 psi 7- 195 psi (COMPRESSION TEST RESULTS)
6- 200 psi 5- 195 psi
4- 215 psi 3- 190 psi
2- 195 psi 1- 180 psi
front of engine

 

Modern spark plugs should last much much longer than 30k miles.

Your test results seem fine to me.

#4 is the worst. It probably crossed the threshold to throw a code, but it looks like #7 is not far behind.

You could try swapping injectors.

 

thanks for the advise. I'm going to swap injectors around today. I hope that's it and not a burnt valve issue.

 

actually cylinder 4 was not misfiring-it had a while back but not recently. I removed both banks of injectors and cleaned them with electronic parts cleaner while applying 12volts to the injectors. . cylinder 7 was the one misfiring. and after swapping injectors in other cylinder locations, and placing the injectors back on engine it continued misfiring. I swapped the spark plug form cylinder 7 with cylinder 1 and cylinder 1 began misfiring where it had not before. I"ll be replacing all plugs. FYI

 

Did this fix the issue?