93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Hey everyone I need help!?! I have a 93 jeep cherokee with a 4.0 high output,the motor has over 200k so I decided its time to find another motor with less miles so my buddy had a wrecked 90 cherokee that is not a high output that had 100k on it,I looked at both motors before I bought it and the only difference in the 2 was they have a different distributor wiring and intake manifold because it had diffent a different throttle body and the wiring harness was different so when I pulled the 2 motors I swapped my 93 intake to the 90 motor and that was no problem that saved changing the throttle linkage and wiring.I never swaped distributors...I also put my 93 tranny on the 90 motor and I know the crank sensor is in the tranny and it worked with my 93 motor cause I had just bought it.Now that I have put the 90 motor in my 93 jeep I have everything bolted up and the only wires on the wiring harnes that would not match up is the distributor wires, the 90 distributor pigtail is round and the 93 pigtail is rectangle,they are both have 3 wires so I spiced them and when I check the spark I only get it on # 2 & 4 cylinders.I have my 93 coil that is runing to the 90 model distributor as well and it is new.I just cant figure out why those 2 cylinders are firing but not the others.If anyone has any idea or anything that can help me please i'm on a dead end road right now.....

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

I believe that fact that you did not swap the distributor is your problem. the 90 motors were renix motors and had different ignition systems. and I also believe that the pick up for the cam sensor in the distributor is different and can't be swapped one for the other. Just splicing in the the "wires" isn't enough. It has to be an equal swap. Remember, it's not a power wire, it's a signal wire. The computer uses that signal from the cam sensor (cam positioning) for timing.

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Thanks for the advice Ponytail,I put my 93 distributor that matches my computer and wiring harness in today , my 93 crank sensor on motor and now I have no spark..I checked the codes and i'm getting a 54 so I guess that means the cam position sensor inside the distributor is bad.I have the rotor pointed #1 and the 1 cylinder is at top dead center so it should be in time.?,?But now I have all my 93 4.0l H.O components on the 90 4.0 non H.O motor.Both blocks are the same,excepted the intake and the distributors.I still have my 93 wiring harness in the jeep,I put my 93 intake and distributor on the 90 motor and all the wires are hooked up and I have no spark.I did have the 90 distributor in the 90 motor but the wiring pigtail would not match up so I spiced them and no matter what combination I tried I could only get fire on #2 & 4.So I put the 93 distributor in and now I have no spark.If there is anyone with any info or have ever seen a problem like this please let me know asap.I will probabley go ahead and put in a new cam sensor in tomorrow and as far as things being new that will be the only thing that I haven't replaced yet,I have even bought another computer.

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 &

What flywheel did you use? The notches in the flywheel (or flex plate) are not interchangeable between the two. If you're running with a 93 setup you need a 93 flexplate. (edit to explain, I mean the notches that the crank position sensor uses, on the outer edge of the flywheel)

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Hmm that might be the problem right there...I am useing the 90 non high put motor with all 93 H.O componets I swaped everything but the flywheel.I put my 93 tranny on the motor as well with a new crank sensor in it.Should I have changed the flywheel?Would that keep me from having spark now?I checked the codes and I get a 54 (cam position sensor)I'm not too sure what the cam sensor does as far as spark?I'm confused on this one>>>

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Hey everyone just seeing if anyone had any ideas on this one...I was hopeing someone had any suggestions as to what I should do.I dont mine pulling the motor back out if I have to thats not a big deal.I never put my 93 flywheel flex plate on my 90 motor and I have been reading that you should change them to complete the swap.Right now everything is bolted up and I have a new cps,coil,cap,rotor,plugs&wire and when I turn the motor i'm not gettin any spark and if you check the codes I get a 54 (cam sensor)I havent replaced it yet because I didnt know if that would keep it from having fire..But would that flywheel keep it from not sparking.I've got alot of knowledge on motors but i'm confused on this one....I just want to fix it asap its been sitting now for a few weeks and I have the next few days off and I plan on having this thing going before the weekend so I can hit the trail I cant stand to see a jeep with no mud on it!

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Hey there, glad to see you found your way over here from Allpar.

Matt's probably onto something on the flywheel - if the notches are too far off, the computer may be too confused to properly time the spark to the cylinders.

IIRC, the CPS watches the flywheel/flexplate to determine the rotational position of the crankshaft, which has to do with ordering spark to the cylinders at the right times to ignite the mixture.

If you don't mind pulling the motor back out, it's probably worth swapping in the 93's flysheel/flexplate to see if it'll help any.

Rob

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Hey Rob thanks for telling me about this site!.I am about to go out and work on it..I was wondering though if that flywheel/flexplate would keep it from sparking,right now I have everything hooked up and everything is new as far as parts execpt for the cam sensor.When I turn the key I have no spark and the code 54 flashes for that cam sensor.Do you think that cam sensor is keeping it from having fire.I woulnt think the flywheel woould keep it from having fire.Or could it,I'm not to sure on what to do at this point as far as getting fire but i'm going to put the flywheel on there if need be.I can see how it would change the timing but I just need some fire first to see how it runs like it is.I need some help on this on!

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

yes, the wrong flywheel would keep it from sparking. I believe the tooth count is different from renix to HO.
It would confuse the PCM, so the PCM wouldn't fire the coil.

You need to have the flywheel that matches your PCM.
likely you're getting that error because the the information from the distributor is not matching the information from the flywheel.

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

Thanks for the advice 87manche man I have been hearing that I need my 93 flywheel/flexplate on my 90 motor.But some people have told me that the 90 flywheel will work but it will run rough.But I have never seen anything like this.Has anyone ever done this swap on this forum?Or had the same problem..I wont to start taking the motor and trans back out I just want to know why no fire.I'm bout ready to take everything apart and start all over I guess. If I need to swap anything else on there why I have everything out someone please let me know.I'm going to start asap if the flywheel is deffent problem.

Re: 93 Cherokee swap, I swaped a 93 4.0l with a 90 4.0 and now only have fire on #2 & 4

I have to agree with everybody I thenk the flywheel is the problem. is the cam sensor out of the 93 or the 90? that could be part of it I think every thing off th h.o. motor needs to be on