1997 GC 3.0 OBD-II P0304 MIL Help!?

[hutch109]

OK, heres the story. The van runs fine, has about 145,000 miles on it - It feels a little rough at idle, but it is NOT noticeable to an ordinary driver... Problem: MIL, small miss, OBD-II PCM code P0304 (Cylinder 4 misfire). History: Attack of the killer woodchuck; ate through the plug wire set. Upon install of the new wire set - noticed an 8-way connector (FI harness) below the coil that had all the wire insulation either worn, melted, or chewed away - still intact - but I am sure some of the wires were touching each other - as there was really no way they could not be. Repairs done: Went to dodge to get new 8-way connector, 1/2 was the set that goes to the 6 injectors, and 1 wire to ASD relay - other 1/2 goes to main wiring harness - fuel injector side, $80.00, harness side connector, $1300.00, my looks and comments to sales-droid... PRICELESS. GRRRRRRRRR....... I remove each wire on the 8-way and use insulated male/FM spade connectors and then electrical tape them up - just like new - and only $6.00 - not $1600.00. I install premium wires, cap, rotor, and NGK platinum plugs. Before the incident it ran fine, and I don't remember a MIL being on. After the woodchuck attack, and post repair, it now starts and runs just fine - I feel slight miss, but nothing I would even notice - had the MIL not been on. I get the P0304 #4 cylinder misfire - so I do some more checking and I pull the upper intake, fuel rail, and other associated parts and pieces and I replace the #4 injector with a brand new unit. Put it all back together, and DRB pressurize the system - only to find out I nicked an o-ring on one of the injectors placing it back in - gas shoots across the shop - GRRRR... Pull the top of the intake off - AGAIN - and pull injectors and re-o-ring them again - this time being really nice, and then DRB pressuring after I put the rail back on - but BEFORE I put the intake all back together - no leak! Yippie. Shew. Start up, runs fine - as usual. After a pair of drive cycles, MIL P0304 comes back - again. GRRRRRRRR.... Reset MIL and swap #4 plug wires - to verify. Re test drive, and P0304 returns. I guess Ill try checking compression later this week - but it runs fine, and the miss is barely noticable. Could the coil be bad? Its only one coil - I can see that being bad, IF it runs fine, and the misfire never changes to another cylinder. I would think either all or none? Am I right? Anyone ever run into this before? I hope the PCM did not get damaged by a possble ground/short on the 8-way FI harness - Ill have to do some more checking. Just trying to see if anyone else has run across this - I don't want keep chasing my tail if someone says "ohh yea - been there done that". I hope I have provided enough info. Thanks! Eric

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[floorslayer1]

What about the possibility of a bad coil pack? A drive mode computer also might help you isolate when and why this occurs. A Snap-On MT2500 would give you drive mode diagnostics, if you know someone you could borrow one from.

[hutch109]

The coil pack was on my list - but I don't understand how it could be bad only on #4; when I have swapped the wires, and it stays with #4 - I would think that the single coil would cause it to either move around, or fail all together - but not stay on the same cylinder. Am I wrong on this thinking? With it staying only on #3, and with all the other secondary ignition and FI being replaced - I am almost left with a feeling of it being an internal engine problem? But since its not that pronounced, or almost non-noticable - it could have also been a damaged PCM by the wiring issue. Ill do some drive tests - I just ordered a brand new scanner to do some more captures. Ill keep everyone posted.

[BNtune]

Yep, been there done that.
My 3.0 with 147K had low compression #4 cyl. 75psi. Leak down test had air coming out ex. burnt valve.
As yours, myeng. ran fine off idle. Mine had same code and cyl.
Could of just taped up the harness.

[BNtune]

BTW no coil pack on 3.0 Just one.