Stumped with erratic miss

[Trooper]

I have replaced almost everything in sensors , a fuel regulator and pump. It only happens every now and then and it NEVER throws a check engine light. What could cause a miss and not throw a code ? Could a injector occasionally miss and not throw a code ? I will take that back I have 204,000 and never replaced injectors. That is the only electrical part not replaced as well as the TCU and speed sensors.

[2000XJ]

Year? Assume that you have a 4.0L (and not the 2.5L)?

Any condition where it occurs most often (ie - sitting in traffic, upon first start-up of the day, etc)?

The more info you provide us, the higher the chances are of us offering you good troubleshooting advice.

[FrankZ]

Bad contact in the CPS connector or partially cut wire causing an intermitant loss of CPS signal. If it happens for less than 90 crank rotations...no code.

BTDT

[Trooper]

Well it used to be after it sat at idle for a while and occasionally a miss down the highway. Now it is to the point that it just bogs and dies on acceleration. It wont start but just crank. When I purge the fuel rail it starts but runs really rough and it backfired once. I have already put a new fuel pump in it as well as the fuel regulator thinking it was going bad which was both wrong. It is not the crank sensor because I swapped my 99 one into the 96 and nothing changed. I also have a new fuel filter and distributor as well. I am throwing a can sensor code , a p1391 ignition code and a coil code. Which have all been replaced. Oh yah I dont have a cam sensor either but the dist. has a stator which is new. Pissed off and just tired of this, nothing I replace makes a difference.

[Trooper]

Sorry 4.0 not 2.5

[FrankZ]

The stator is the cam position sensor.

Can you provide all 3 codes please.

[BlueXJ]

Codes would help alot. The purging of the fuel rail is interesting as well. Were you getting air or foamy fuel from it? Sounds like a loss of pressure from an unknown source. Any ideas about that Frank?

[2000XJ]

Cylinder Misfire codes would be P0300 (General Cylinder Misfire), P0301 (Misfire on Cyl 1), P0302 (Misfire on Cyl 2), .... P0306 (Misfire on Cyl 6). Not sure what the other code could be.....

Good question Blue

[BlueXJ]

Knew it was a good question but would like the OP to check in so he can answer it.

[FrankZ]

There's a TSB out there that addresses some of this. I'll find it.

[FrankZ]

Here ya go...
Jeep 4.0 multiple cylinder msfire TSB - Multiple, possible, and cylinder

[Trooper]

Here is exactly what my scanner says

P0340 Camshaft position sensor A-Bank 1 circuit malfunction
P0351-Ignition coil A Primary/Secondary circuit malfunction
P1391-Ignition system or misfire Manufacturer Control


Again the distributor is new, coil, fuel pump, fuel regulator, and all sensors on the throttle body as well have been replaced. Thanks to all for your help.

[Trooper]

The bullitin is for 99 to 01. Mine is a 96. when I purge it the gas kind of comes out in either a quick shot or a quick shot and comes out like a slow faucet for a while. I have already replaced the ignition switch as well and the starter is new and hell i can keep going on and on lol. To me it almost appears to be that the injectors arent working right. I know i have good spark, the ignition switch is starting or turning it over and the pump is definately working as well as the new regulator that went in a few days ago. I figured it was the regulator going bad and sending too much fuel to the injectors and causing it to bog. It only made sense after I turned it over a few times after purging it a few times it would start. I swear JEEP stands for JUMPS EVERYTHING EXCEPT PAYDAY.

[jimmydabull]

Mine just started having the EXACT same issue today. It does seem like it's getting "flooded" as it doesn't start right away after it happens. If I let it sit for 3 minutes, it starts and is fine for awhile...I'd pull my hair out if I didn't shave it! LOL

This is seperates Jeep owners from everyone else! Time to dig....

[Trooper]

I am completly stumped at this time.