Bad Miss in #5

[BADASYJ]

It all started when I Overheated the jeep and blew my head gasket. When I started it back up it had a miss, I figured it was due to the blown head gasket but the miss remains after rebuild. I Melted two pistons, #2 and #5. Replaced both pistons std. size re-ringed every piston and new rod bearings also. The head had a fresh valve job before the meltdown. Afterwards I had it shaved .012 cause it warped, also had it magnafluxed for cracks , it came back good. Now it has a bad miss in #5 cylinder I Switched injectors, plug, plug wires, and shimmed rockers on #5, but the miss remains in the #5 cylinder. The cylinder is getting spark. I am getting codes 21, 27 twice, and 43. Which I think the miss is causing the codes.
Any help would be appreciated.
Could this be a cracked head? Maybe between the exhust and intake runners?

[yjcrawler86]

have you checked the compression in that cylinder?

[YJason]

I had the same problem on #1, it was a valve sticking. good luck

[Cheromaniac]

Hope this helps:

Code 21 Oxygen sensor reporting too lean or too rich after 2 – 12 minutes with temp over 170° and RPM above 1500
Code 27 Turbo engine injector driver circuit two shorted or open
Code 43 Ignition coil driver circuit open or shorted

[SilverXJ]

From the codes is looks like a bad injector or coil.. but you already switched out the injector.. what about checking the wiring to that injector? Doesn't really sound like the coil as it is isolated to a single cylinder.

[BADASYJ]

The cylinder only has 55psi on the compression test. I'm leaning toward a cracked head. The head I have is the 0630 not sure if this head or the newer head had the cracking problem. But no water in the oil. Could it have cracked between the intake and exhust runners? Looks like I might be rebuilding the spare 7120 head.

[IH 392]

You said it had a valve job BEFORE the melted piston?, did anyone pull the valves AFTER the meltdown!?, sounds like to me like there is some aluminum on the seat holding it open?