First of all thanks for allowing me to become a member here. My latest project had a friend of mine direct me to a thread here, but it doesn't seem to 100% apply to my cherokee.

Vehicle: 1994 Cherokee, 4.0, AW4, 242, 30/8.25. 153k miles on it. I paid very little for this thing, and have learned a great deal about it since dragging it home in the super summer of 2011. When I bought it I had no spark, swapped out the CPS, and spark was there. Then no fuel, so I have swapped out the fuel pump, and fuel at the rail. During some routine maintenance that was needing addressed, I had to pull and swap the dizzy. Somewhere along the line I don't believe that I got it back into a position that makes it run like it should. Swapping out the dizzy got me a replacement cam sensor, and so I did the cap, and rotor also at the same time.

Issue(s): Very hard to start, rough to little idle, no real acceleration when throttle is applied, and when put into gear it wont travel faster than 15mph(during two separate test drives).

Items replaced that were tested as bad: Crank Sensor, Cam Sensor, CPU, Distributor, which had a ton of side to side play in it, which wore the cam sensor out. I have also replaced the spark plugs and wires(already had new ones on hand from a previous XJ).

I have been told that the IAC is a likely culprit, and I have pulled and cleaned that totally up. I just pulled the throttle body off and cleaned it all up and am in the process of putting it back together and on the Jeep.

Questions: Is there a way to test the IAC, either electrically, or diagnostically?? I have run the TPS through a couple of tests, and the FSM(yes I own an FSM for all my vehicles), doesn't list a test procedure for the IAC. This thing when warm is fine restarting, but I am wondering if I have the Dizzy off a tooth still or what? Cold starting is a problem with this, and I am trying to make less of a hodgepodge Jeep and more of a DD out of it. I need to replace the entire exhaust system, as the tailpipe starts at the drop in front of the rear axle and thats it, I just cut the Cat out, so I can stop the rattling to hear other issues, and now its just the front half of the pipe only. Plan is to replace the entire exhaust from the header to the tailpipe end. But until I can get the rest of the engine working together I am at a standstill.

I want to guess that this video might help: http://youtu.be/739IlxuI_iY

Any thoughts or input here will help. I have learned more about FI in the last 6 months than I have learned in the last 12 years owning an XJ. Thanks in advance,

Jeff

 

I don't know of an effective way to test the IAC, it's a stepper motor that notches the valve open/closed on command. Test by substitution is probably simplest.
There is a procedure I've seen posted here to index the distributor, although I don't know if it applies to your era Jeep. Might not hurt to search it up. "index distributor" should do it.

What sort of tests have you run on the TPS? Have you checked fuel pressure with an actual gauge?

 

I really don't think you can get the dizzy off one tooth they have a slot on the end and you either get it in right or 180* out but then it back fire through the TB. Its hard to tell on the video since you have no exhaust, have you checked for codes?

 

No codes pertaining to any emission or engine management stuff right now. I had read somewhere that off one tooth can make easy to start and run rough, off one tooth the other, hard to start and runs fine. I want easy start and runs good. I have tried and tried to set it to the FSM, and when that is done, it hasn't restarted. A guy locally to me indicated to pull the IAC from the TB, and plug the hole, fire it up and see if that does it. This thing has had some issues from the get go, and while I don't want to just throw money at it, I am also trying to see if others or anyone else has had a similar problem, or how they got down to diagnosing the IAC as being a hard start/rough idle issue. I have read through the threads here, but I have also been posting this issue locally to me, and on NAXJA forum as well. I have gotten more of a response here vs anywhere else. The video was taken prior to the hard to start condition that has been persistant, since the temps dropping, and a partial cleaning of the IAC and its passages. Since my post, I have cleaned the IAC passages, as well as the TB, and there wasn't any change to the starting, I did get it running some, but it was real rough, and upon application of the throttle, really didn't throttle up much, but after maybe a min of holding the throttle steady, it evened out some. I am trying to rule out simple stuff prior to doing more advanced diagnosis of it, like compression testing, as well as replacing the entire exhaust system from front to back, as all components are shot, and I am beginning to think maybe the O2 sensor is shot which also could be a culprit here, if there is a leak in the manifold which I am betting there probably is. Keep ideas coming as I keep checking components to verify they are or are not within specs.

Jeff

 

When you say you "swapped out the dizzy" did you get a J/Y one or new?

 

Got a parts store replacement one.

 

Maybe buy a New TPS and put it in there to see if any changes. Keep it clean and undamaged and you could always return it if it doesn't help the idle and roughness.

 

Question still, will a bad TPS cause a hard/no start condition?? I wasp lambing on replacing it at some point, because I know it's not within the specs the FSM states. Still not starting, and now it's likely gonna need a starter with all the cranking I've been doing. The IAC is also probably shot, since when I was trying to crank it during some testing the end came off, so it's gonna be replaced as well. I was checking it for proper operation. Well I believe it was.

 

Here is a slow to come update. I have replaced the TPS, restabbed the dizzy several more times. Still not starting. I tested the fuel system pressure, its around 31psi when the key is first turned on. During cranking, it goes up to 40 psi. After letting off the starter, it drops down to about 34psi. All plug wires are in the correct positions, and all are getting spark. What else should I be checking?? I am going to start restabbing the dizzy now, till I get a position that yields me a starting, running specimen. Thoughts on something that I am missing as well??

 

Here is a video on me trying to start it:

http://youtu.be/m5pR0orJ9eM