91eXJa

I have a 91 Cherokee, though the engine has been swapped to a 96, not sure why, bought it that way unknowingly. The computer is still from a 91, at least OBD-I. But the distributor is off a 96, I know they are different between the 91 and 96 but does anyone know if they should work. It starts fine and idles beautifully, but it falls on its face when accelerating, feels like fuel or spark is completely shut off, and don't have to accelerate hard for it to act up. Vacuum is a bit low at idle...13-14hg, right about 19 when cruising at 1500rpm. Fuel pressure is beautiful, o2 sensor is new, MAP is good, coolant temp sensor is good, air temp sensor is good, distributor/cam sensor is new (96), plugs, wires, cap, rotor all new.

Any ideas??

Nicks90xj

mabe cloged cat? does it do it all the time? hot or cold?

Precept

I have a 91 cherokee with a 94 engine. It was installed because the original engine was leaking oil profusely and the 94 engine from the wrecking yard was cheaper than rebuilding the original engine. The manifolds, throttle body are all 94 (came with the engine I presume, as I was not the owner at the time). My jeep runs really good. I must tell you that I also had to replace the catalyic converter in order to get the jeep to run. If you disconnect the 4 bolts that hold the converter to the exhaust pipe (engine side) and lower the converter away from the exhaust pipe, the engine should run much better (if the converter and/or muffler were plugged up.

91eXJa

That is the weird thing, it used to act up worse when cold and run "ok" when hot, now it is the opposite, seems "ok" when cold and pretty bad once warmed up. I have not checked the cat but it doesn't feel like that to me because usually with a clogged cat, the engine is usually trying, (I may be mistaken on that) but mine doesn't have any power when it is acting up, cuts in and out hard.

gajeepguy

I don't think a clogged cat would cause it to cut in/out? I dunno though. A totally different animal, but my diesel had a clogged cat from letting it idle in the mornings while I got ready, anyway it ran fine you'd never really notice it unless trying to accelerate hard, tow, or go up a hill--then it was a complete dog (like it had 10hp) but it still ran fine.

I imagine that an OBDI and an OBDII distributor are not compatible? I think you are on the right track.

Err... myabe not found this long read but http://www.xjtalk.com/showthread.php?t=9111

Are all of the other sensors and wiring from the 91 or 96?

91eXJa

Thanks for the link, haven't read it yet though. As for the sensors, I cross referenced them between a 91 and 96. The MAP, O2, coolant temp, air temp, plugs, and wires are the same between the two...

Nicks90xj

have you checked compression at all?

cruiser54

Has it always done this with the later engine or is this something new?

91eXJa

Yes, compression is good, 160-170 on all cylinder's.

I don't think it always did it. I didn't swap the motor, the PO did, it didn't drive like this when I bought it, on either of the test drives or for a while after I bought it. I only bought it about 7 months ago or so. I didn't drive it very much when I first got it though, had to do some work on it first.

grizbomb

did you try cycling you key on off 3 times see if there are and trouble codes in the computer? that may help you start looking in the right direction

91eXJa

Yes, the only code is a 62 if I remember correctly, which has something to do with mileage memory for the maintenance light or something like that...

sthon

I would try reindexing the distributor, it could be a tooth off.

91eXJa

Yeah, I am going to mess with the distributor this weekend, see if I can come up with something. Maybe advance timing (use a different hold down) or what. I'm pretty sure it wouldn't idle as beautifully as it does if the dizzy was a tooth off though...?

cruiser54

You won't change the tinming no matter what you do. I can't see how the dizzy became "un-indexed".
Here's how to verify it's indexed properly.


http://www.angelfire.com/my/fan/dist_index.html

sthon

Obviously it can't on it's own. It is possible to put it in a tooth off either direction. Probably not the problem since it idles smooth, but it's free to check and takes all of 5 minutes.