• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Misfire cylinder 5

When my 2000 started doing the same thing, it turned out to be the wiring harness. It wasn't until I tore into the harness that you could tell what was happening. Previously during point to point testing all showed good, it was insulation breakdown that allowed shorting between the injectors. The O2 sensor wiring didn't look any better.
 
that is interesting and I have thought about the harness. My shop said they can me a new recreated one for $1200. Wish I kept mine from my last part out, that jeep was in great shape.

I did open up the loom from the injectors to the PCM. everything traced to the injector and looked OK. I mean the wires by the connectors look questionable on everything...

looks like I might have to try a junk yard harness. thanks for the comment, i appreciate it more than you know.
 
Looks like I might be missing the grounding strap between the firewall and the head/stud. Reading more about my issues this sounds like it might be the or part of the larger issue. Going to slap one on this weekend and will see how it goes.
 
Mystery solved. #6 tube is cracked on the exhaust manifold. Hooked up the shop vac and could feel the air, sure enough about a 1.5" long crack.

It is pointed right at the #5 intake just below the injector.

Is this a bad idea, your potentially throwing debris into the engine,no?
 
So the engine is running much better and not misfire codes but still getting the p0122, low voltage tps A circuit.

I tested voltage with the key on and tps has .01 at the ground, .85v at the signal and 5.11v for the input.

I get the code with the engine in the on position and the engine off. If I start the enginge and clear the code it does not come back on. Only with the key in the on position. This has been very consistent.

I read the clockspring shares the same 5volt ciruit and I pulled the horn relay. No dash light for check engine but it throws the code on the scanner
 
Did you try putting the stock injectors back in? I had this issue when I went to 4/12 hole injectors. issue resolved immediately when I went back to the ones that came in the jeep. the 4/12 holes are skinny, plastic, less metal to dissipate heat under in hot engine bay, ecu was not designed for them either. worth a try if you haven't.
 
Interesting. I'll see if I can dig up my old injectors. I ruled them out after swapping them and not changing the original misfire.

The misfire is gone now for the most part, seems to have been a grounding issue. I still have a low vacuum I need to track down
 
Ok so now I jumped the grounds for the obd2 and ??? that go to the engine block by connecting a lead from the bolt to the neg battery.

Now I get p0123 high voltage which I confirmed, running between .9 and 1.3v at idle engine running.

Anyone know how likely it is to be the clockspring vs a short?
 
Back
Top