Hi guys! I recently got a new job as a rural carrier with USPS, so I went out and purchased a factory RHD 1997 XJ 4.0 automatic with only 95k miles on the body and motor. The first day I got it, I drove it for about an hour and a half flawlessly, no check engine light on, no problems running and plenty of power. Then it just shut completely off on the interstate, so I trailered it home.

I assumed it was the typical XJ crank sensor problem, so I put one on it from AutoZone (Duralast lifetime warranty). Nothing. Eventually I figured out the gears on the distributor were ruined. So, I put on a new distributor, and she started up although it was a pretty hard start. I noticed it had a slight miss and after letting it run for 20 mins or so, I went ahead and did all new plugs and wires. Typical Champion coppers (gapped correctly) the 4.0's love, and new Duralast wires since the old ones were pretty crap anyway.

So it runs now but it's still missing and not only at idle, but also once I hit about 2k RPMs it'll start to miss a little harder. It's hard to take off from a stop with it being right in the power band, and once in a while it will give a couple small backfires through the exhaust. I told my buddy that's a mechanic (runs his own shop not like a self proclaimed backyard mechanic). He noticed that the distributor has a very, very slight shake to it, to where I just assumed it was because the Jeep was running. He seems to think that it needs a new camshaft, and that cranking it over for a little after trying things to fix it has ruined it, and that's causing the misfiring. Now, I'm here because I want to know if you think that's a real possibility, or if you think it's more likely something else.


Here's what throws me: Generally, the first time I start it, it still has slight misses here and there, but it runs 100% fine otherwise. Full power band, I can give it gas and it'll downshift and go right up in the RPMs and accelerate no issue whatsoever, and then all of a sudden it will start doing it again, and will continue to any other time I drive the Jeep that day. It has nothing to do with the engine being at operating temperature because sometimes it starts the missing in say 5 minutes, and sometimes it'll drive perfect for 30 minutes then start doing it. I've seen MANY people talk about having trouble with using a non-Mopar branded crank sensor. Do you guys think that could cause my issues? Hard start, missing at idle and in rev range, and small backfires? It has never once stalled on me since I changed the distributor.

I used the ignition trick to get codes because it does have a check engine light. The code that came up was 11, which is "No crank reference signal detected during engine cranking. Intermittent loss of either camshaft or crankshaft position sensor." I'm just trying to get some opinions before I go through the trouble of putting the original crank sensor back on.

 

I think you need to double-check that you have the distributor indexed correctly.

 

 

See, I thought about that as well while I was at my friend's shop, I asked the mechanic that is always there to help him if it was a possibility and he said no and that he highly doubts that. They both seem dead set on it needing a camshaft. I'm going to give re-indexing a try before anything else. Thanks guys.

 

I can almost guarantee it doesnt need a new cam. I think its time to find yourself a different mechanic. Start with the timing and go from there.

 

Unless your mechanic works a lot on vintage Cherokee XJs, he probably doesn't know much more about that vehicle than you do.
Jumping right to the conclusion of needing a cam shaft is just bad diagnostic work, regardless of vehicle type. Even if the distributor was vibrating, it would be more likely that that the distributor is defective then the cam.
Maybe if the computer would throw a code that told them exactly what to do it would help them. lol. But it's not going to do that.

 

If it was running fine then unless something catastrophic happened it's just basics.
First mistake you made was Duralast crank sensor. Only Mopar will work here, zillion threads on that, the magnets are not strong enough. Been through this myself and seen first hand, even more so with the cam sensors..
Second, check fuel pressure. This should have been first.
Third, if you think you might need a cam sensor, get a mopar from a junkyard instead of dropping $90. Chances are slim but it could be.