RoadWarrior00

Recently purchased my '89 Cherokee Laredo. Engine was supposedly rebuilt about 5 months ago.

It has a low idle and stumbles and dies if step on accelerator to quick. Several other issues as well, but want to figure this one out first. Following is a list of other known issues in case someone might think they relate to idle problem.
1) Freeze plug behind bellhousing leaking coolant slightly.
2) Power steering leaking and sometimes makes noise/sometimes doesn't.
3) 3 Vacuum lines were disconnected from 4WD controller that is on axle behind passenger front tire. I reconnected them like are on my '88 and had mechanic check the 4 Wheel drive. He said 4WD wasn't working this morning. I may have connected vacuum lines incorrectly and/or mechanic said lines/controller may be junked up from being disconnected.
4) There were a few wires that insulation had been striped from and a couple that had been cut and just twisted back together. I made sure wires were still good, connected well, and wrapped with electrical tape. Could wires, if not full solid wire with no repairs, possibly be cause/part of problem.
5) Runs cool and mechanic says thermostat probably missing or stuck open.


As for the Idle problem, I have checked many things and took it to a shop to see if they could figure it out but he couldn't figure out problem either. I also have an '88 Base XJ(also I6,4x4 w/ auto) that I am using for parts swap/testing.

THINGS I HAVE DONE/TRIED:
1) New Battery
2) Swapped Coil & Module from the '88.(No Change)
3) Swapped MAP Sensor. (No Change)
4) Checked for vacuum leaks. (None noticed)
5) Replaced Air Filter. (No Change)
6) Replaced Fuel Filter. (No Change)
7) Shop Tested Fuel Pressure. (Said it was OK)
8) Shop hooked up machine and said only problem found was TPS was not reading right. Said he adjusted it but don't know at moment if he got it to read OK or not. Going to pick car up from him today and will ask him for more specific info and report back here.
9) Don't know if means anything but I found that if I remove one of the 2 vacuum lines from the connector that has a line going from top of it to the fuel pressure regulator, the idle jumps up to around 1100-1300 which keeps it from stalling at idle, but still stumbles/stalls when press accelerator. If hook the mentioned disconnected vacuum line back up while car is running, car dies immediately.
10) Mechanic told me when he called to say he couldn't figure it out that he did notice a freeze plug behind bellhousing on block is leaking coolant a little. I don't imagine that would cause idle problem though.


Guess that's about it for now. Will provide more information as discovered.

ANY help appreciated. THANKS!!!!

RoadWarrior00

OK, I picked up car from mechanic and asked for details on TPS check.

He said testing from sensor itself he got it adjusted to spec., which tells me TPS is good, correct? However, he said ECU wasn't sensing throttle change according to diagnostic machine. He said ECU wasn't sending signals to necessary systems to change air/fuel mix when depressing throttle.

This tells me there is either a break/short in signal wire between TPS and ECU or ECU itself is bad. Is this a reasonable assumption or can someone think of anything else that may disrupt signal between sensor and ECU. Alternatively, is there maybe another sensor that also needs to supply info to ECU in order for it to adjust air/fuel mix correctly besides TPS or something.

If it's a bad ECU, would the ECU out of my '88 work? Same transmission, Engine and both are 4 wheel drive. However, the '88 is a base model that doesn't have any extras like PW, PL, Cruise, etc..., which the Laredo does. Do all those extras run through the ECU? If so, did they perhaps use same computer, just all the extras not hooked up to ECU in base model? Or if would work but maybe just lose like the cruise control or something, I could live without it. Could I use '88 ECU in the '89 to just check to see if it corrects idle/acceleration problem so I would know if the '89 ECU is bad or not?

Sorry for all the questions!! Just trying to get this figured out so I can be mobile again.

RoadWarrior00

No ideas anybody?

A_Jeepr

I got a 89 Laredo, only power option on it is power steering, no cruise or a/c. I by passed some vacuum lines to make 4wd always work when I tell it. Removed the EVAP charcoal canister and done some other things to it. Runs at 750 idle all the time no problems.

it sounds link a loose injector, replace the o-rings on the injectors and see if that helps.

RoadWarrior00

OK, I will try that. THANKS!!

Any way to judge how snug they should be?

mike albo

Did you check the IAC in all that?

A_Jeepr

it there is any leak or tear in the o rings it will allow extra air to enter the cylinder, causing the o2 sensor to get confused, and mess with the other sensors, and cause it to idle funky.

RoadWarrior00

NO. I asked the mechanic about the IAC and he said he didn't think that was the problem. Don't think he was willing to do much to try and find the problem. He recommended a local shop that specializes in Jeeps and 4x4's, but they said it would be at least 2 weeks, maybe a month before they could look at it. HARD TO FIND A GOOD SHOP THESE DAYS!!!

Might try to check it myself but I don't have many tools on hand to work with.

RoadWarrior00

Assuming your referring to the injector Orings, I looked them over pretty good and checked how they were sitting compared to my '88. They seemed OK. The wire connectors seem really lose to me(no resistance whatsoever), but I asked the mechanic and he said they don't fit real tight. 1 or 2 of the connectors are missing part of the plastic on bottom so can't even put the little metal clip on them, but their not popping of or anything. Thought about trying to use needle nose or something and pinch wire connector terminals so fit snugger but was afraid might break already fragile connectors. Also thought about cutting injector wires from 88 and putting them on the '89, but didn't know if using cut/spliced wires would affect injector functionability.

If Orings were leaking wouldn't it spray fuel out from around faulty ring?

Pardon my ignorance, but I'm somewhat new at this other than normal maintenance stuff. So, I appreciate everyone's input!!

RoadWarrior00

Well, probably don't have to worry about problem anymore. Someone rearended me today. Guessing as old as car is insurance will probably junk it, just hope they at least give me close to what I paid for it.

Gotta say though, these Cherokees are some tough little *****'s. Guy musta nailed it doing about 35-40 MPH and all it did was just push rear bumper in. Mighta done frame damage that I couldn't see though, don't know yet. Smashed the whole front of his big old 4 door pontiac bonneville looking car in.

SO, ANYONE IN MY AREA GOT A DECENT USED CHEROKEE THEY WANNA SELL IF/WHEN I GET INSURANCE MONEY!!!