I swapped in a 5.9 magnum into my Jeep Wrangler about 6 months back. I have yet to get it running right. For the past 3 months its been on the back burner since I bought my 94 Supra. But now I have the motivation to get it back on the road and running right.

Some background info: Motor was from a 98 ram, or so I thought. The pcm was for a 96, and it has a mixture of 96 and 98 harness plugs. The Jeep is a 2000.

The Issue: While idling it will randomly start to open the IAC pintle to fully open and it will idle low and stall unless I give it gas. It appears to only happen in closed loop if my memory serves correct. I've replaced the IAC, CKPS, CPS, TPS, O2, Ign. coil, spark plugs, wires, distributor, and MAP. All my grounds are good. I've cleaned the throttle body, and replaced the plenum gasket and fixed a vacuum leak. Could the ECT or IAT be causing this?

I figure the pcm starts to read its running to rich at idle, then trys to allow more air in but in reality it was at the right mixture and it leans out to much causing it to stall. Am I on the right track?

I also have a stalling issue while driving. It will randomly lose spark. It ran perfect for about 2 weeks, other than the idle issue. Then out of nowhere it just started stalling out again while driving. I've checked all my grounds and they are good. All the ign related items are new. ASD circuit checks out okay. Also, it was running fine for about 1 week as well, then I had the upper rad hose develop a crack, and sprayed coolant everywhere. Got it fixed, but it I couldn't get it to start back up. Turned out the battery was low. Got a jump and started up, but would stall after a couple minutes. Got the battery charged and tested and still stalled out. Could something have been shorted by the hot coolant spraying everywhere? I replaced the ign coil after this but didnt fix anything.

Now, after it had been sitting for a while, I started it up a week ago. It ran fine but still had the idle issue. I've yet to take it on the road to see if it stalls, but just sitting in the garage and imitating driving by revving the motor, and holding it at certain rpms it ran fine.

And! one last issue... if I floored it while driving it wouldnt go anywhere like the clutch was slipping. My tranny is a nv3500. Brand new clutch and flywheel. Did the proper break in period. It is a clutch for a 5.9 dakota from autozone. Could it just be a crappy clutch?

Sorry for the long post, but I'm ready to get this thing back up and running.

 

What brand replacement sensors did you install? Did you address the plenum issue? And did you check the cat? Sounds like it might be clogged.

 

I used a dealer items for the CKPS and CPS. Then a mix of napa and advanced for the rest. I didn't go with the cheapo sensors. I'm just running block hugger headers with a flowmaster. No cat. I did fix the plenum issue. Felpro gaskets all around.

 

No cat, Hmm. What about the plenum(lower intake gasket). If it's blown the o2 may be bad already. (even if you have no codes). And how come the PCM swap? What motor was in the Jeep originally?

 

I replaced that aswell. I did not replace the o2 after the gasket swap. Well, the motor came with the pcm and wiring harness. I did the swap myself, it originally had the I6. I've found the seller was very dishonest. He even gave me the flywheel that was supposedly with it and claimed it was a manual tranny pcm. PCM is for an auto, and the flywheel was for the older magnum motors, didnt have the tone ring.

 

I think I'd get a PCM for a V8 out of a Jeep of the same year as yours and as close to the same options you have on yours. And harness for that matter. A 96 PCM is not going to like being installed on a 2000. And there are some small differences. Like Coolant temp sensor. A 96 has two and a 2000 has one.

 

Okay, I was planning on getting a new pcm soon since this one cant run my gauges. So I have aftermarket gauges I got from a friend right now. I will see about getting a wire harness and pcm from a Jeep Grand that had the 5.9. I know it would make things easier. I looked for one for the longest time but couldn't find one so I just went ahead and did the swap and sorted through the wiring mess.

 

Yea, you got to get the PCM and harness changed before trying to troubleshoot any further. I could be wrong, but if you still have the original PCM, a dealer might be able to flash it for a v8. Then all you need is the correct harness.