Hey all, having a new issue where my Jeep is misfiring while I drive. Starts up great, but as soon as I try to drive it it starts to run rough. The coil pack is brand new, the plugs are new, injectors are new, cam shaft position sensor is new, not really sure what else it could be. The parts store checked the light and the code I have right now is PO353, and they suggested the CSP sensor which as I said was just changed. Only thing I can think of is to check the connections for the coil pack since I did have to redo them when I put this motor in. They looked fine when I swapped the coil pack, but I am going to take them apart and redo them again tomorrow I think. Hopefully you all have a suggestion for me. Thanks for any advice or help.

 

Just so you'll know, the cam sensor times the injector cycle, not the ignition timing. When you changed the cam sensor, did you pull the drive unit out, or just the switch on top? If you pulled the drive, you'll have to retime it. To get that right, you'll need a DRB scan tool to fine tune it. You can get it close using a toothpick in the index hole in the case.

 

No I only pulled the switch on top. It was running great for a few days after I swapped that, no issue. Even took a 500 mile round trip in it

 

What brand of coil pack did you install? They have been known to fail right out of the box. They will short internally because of the long connector links inside. For instance, coil #1 fires cylinders #1 and #6 at the same time.

 

The coil pack I had on it was Omix Ada from Quadratech, which wasn't too old but I swapped it with a Duralast seeing as the symptoms it was giving me indicated that was the issue. I don't think it was that though as the problem continued after the swap.

 

Well, your getting a coil 3# primary circuit fault over multiple coil packs so I'm guessing a wiring fault somewhere between the connector and the PCM, possibly, but not likely the digital driver inside the PCM. Check the PCM cable connector for a corroded pin. Also look at the wire bundle that goes behind the head for a chaffed wire.

 

Reporting back; it was the connection from the harness to the coil pack. I had to get the soldering gun out, fix the connections, and all is gravy now.

 

Electrical diagnosis is a simple matter of checking various points in a circuit for good connections and available power at various points in that circuit. If that all checks out, chances are the component is the problem. Remember the ground part of the circuit is often overlooked. Corrosion in a connector is a big problem. It can cause resistance heating and actually melt the connector without blowing the fuse.

BTW, Happy New Year!