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Discussion Starter #1
Ok so let's start off, I'm new here and just wanna figure this problem out. So let's start with this, I rebuilt my 2001 4.0l grand cherokee motor about 3000 miles ago, everything internal in the block is brand new, bored it out 30 over because I lost piston number 1. I had the head resurfaced and used the old one, little did I know it was cracked but I will get to that. Got it running and was running fine for about 2000 miles, finally figured out the head was cracked so bad it had to be replaced. I got a recast of the imfomis 0331 head, it has a thicker deck, put new springs, valves, it already had new rods and rockets. So theres a little back story, finally got it all back together started it up and it was running fine for about 45 minutes while my mechanic buddy was there, of course he leaves and it starts misfiring. I changed a map sensor, put a new ignition coil on it, replaced the injector that said it was misfiring on, put new spark plugs on, have sprayed brake clean to find any vaccum leak and nothing. I'm stumped and can not for the life of me figure this out. Im about to throw my hands up and take it to a shop. Please help me jeep community I would really appreciate it.
 

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Monday morning quarter backing, too bad you didn't upgrade that crack prone stock head when the engine was rebuilt.
Anyhow, i assume its throwing a misfire CEL on one cylinder based on what you've said?
Or are there CELs pointing to multiple cylinders?

When you pulled the plugs does the misfired cylinder plug look wet, fouled, bone dry, etc.?

My two experiences with 4.0 misfires.
I hate that long gang banger coil pack on these later year 4.0s.
One time after replacing the plugs on my XJ, one of the coil pack's contact/boot totally missed the plug causing a misfire situation. Also makes trouble shooting a PITA not being able to easily verify if a cylinder is getting spark.

The other time was when my old '94 XJ had intermittent misfires. Turned out the injector harness was shorting out.
Check that injector connector and the harness real close.

If you had a diagnostic test scanner or one available this would be a lot easier to trouble shoot.
 

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Discussion Starter #3 (Edited)
I just pulled the spark plug on cylinder number 2 and it was wet with gas still, like it's not even firing at all because all the other plugs are dry
 

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Well there you go, likely no spark on #2.
Since you replaced the #2 injector and assuming its good and the correct P/N i'd still ohm out its solenoid coil to be 100% sure.
Then its has to be either the harness, Injector connector or hopefully not the PCM.

I'd double check the injector connector for bent pins, spread pins, corroded pins or burnt pins and if all that looks good i'd pull apart the injector harness to check for any obvious open circuit or short circuit'd wires concentrating on the #2 wire(s).
You can check the source at the PCM that its properly firing that injector with a DVM and a straight pin but only if you know what you're doing and have a PCM schematic pin out.

Like i said i had misfires on my old '94 XJ 4.0 which was the injector harness near the firewall with some of the wires had frayed insulation and shorting out usually only when the engine was hot.
Could be while rebuilding the engine the harness or some connector got hosed somehow and finally crapped out.

Keep us updated.
 

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Ok, i got carried away with the injector stuff which according to the OPer is likely not the issue since #2 plug is wet.
The issue is likely no spark on #2.

Since you replaced the coil pack, the only other thing is probably its connector, an open wire or shorted wire in its harness.
Double check the coil pack is electrically engaging with #2 spark plug.
 
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