2002 denali 6.0 p0304

[billywhoa]

checked plugs, power to injector with noid lite, leaks at intake manifold with wd40 and water , nothing. also p0430 code catalyc bad was there before this code. didnt replace cat yet.

[GM-Tech]

It takes a pretty severe, consistent misfire to set a code for a specific cylinder misfire. Most misfires will just set a P0300. If you did/do have a bad miss, the cat is no doubt toast by now. It doesn't take too much to damage the cat when you have a severe misfire.

 

You may have injector pulse, but is any fuel getting through the injector. Need to do an injector pressure drop test to see if it's flowing as much fuel as the others. I've also seen clogged cats cause a pretty severe misfire, so which came first, the misfire of the cat problem?