thunderwasp

2000 jeep cherokee 4.0L

My jeep has P0300, P0301, and P0305. The problem is that when I pull the injector wires, cylinder 1 and 5 are firing. Cylinder 2 never fires but doesn't give a code. What is causing this???? Also it runs way worse when hot-mostly after a hot restart. It is hardly driveable then and flashes the CEL. I can drive it for awhile from a cold start if I don't shut it off but it still idles rough. If I let it set for 20 min and then restart it hot it runs really bad and CEL flashing.

I've replaced:
1. cylinder head- used from junk yard
2. coil
3. spark plugs
4. fuel injectors
5. O2 sensors
6. intake manifold- used from junkyard

My original cylinder head was cracked between valves on #1 cylinder and my intake was cracked around the mounting flange around #6 cylinder.
With the original head on compression was good (135-145 dry) except on #1 it had 100psi but I figured that was due to the crack. I haven't checked it again since putting the junkyard head on.

I'm really beginning to think this problem is impossible to fix. Why doesn't the computer throw a P0302? Why does it give the p0301/p0305 when they are firing. I'm really frustrated. I guess I'm going to part it out soon but hate too because I've got so much money tied in it. I could really use some help. thanks