Need new computer for 87 Comanche long bed

[Kesswic]

Howdy y'all,

 

I need some advice oh how to get a new computer for my 4.0, 2WRD, 87 MJ. I've been having issues with my MJ starting for years and it's finally given up on me. The machanic told me that the computer in the engine is fried, power is going to the computer, but no power is going out is what he explained to me.  I'm up $#!& creek without a paddle because I lack the know how of working on engines and anything electrical. My MJ is my daily and I van life out of it so I'm trying to get it fixed as soon as I can. Where can I find info about the computer in my engine or other information that may help me?

 

I'm sorry if I'm missing any info, I'm new to this forum thing and working on jeeps in general. 

 

Thank you for your time and patience.

 

 

 

 

[87MJTIM]

Where in VA?

[jpnjim]

I've never had a Renix computer go bad on me (yet),

 but is your mechanic pretty sure that whatever caused the last one to fry won't blow up the next one too?

[Airborne Janitor]

What are the issues your truck is having exactly? Was it running well before it wouldn't start? Hard start, rough starts? How did it drive?

[The86manche]

If you do end up needing an ecu there's one in an 89 in a local yard to me. But I'm in mass. I Can get it and ship it to you

[cruiser54]

I'm not convinced it's the ECU. How much diagnostic time did the mechanic invest in this?

 

I have an 87 ECU. 

[Kesswic]

Thank you all for the info!

 

I'm currently in Key West, not VA, and the machanic I went too didn't tell me much. All he said was the computer was fried and wouldn't explain further when I asked him.

 

As far as starting goes it used to be fine, but the longer I had it the more often it would give me problems. I have fire and oxygen, but the engine won't kick over. I've replaced everything in the ignition process from spark plugs, starter, starter sensor, distributor, alternator (twice), and multiple sensors.

 

I went to pick it up yesterday and it magically started, but when I took my foot off the gas is cut itself off. When I started it a second time it had a very deep sounding exhaust and engine (I haven't done anything to make them louder on my own.) but it was able to drive itself home about a mile away.

 

I'll look into the info y'all have me, hopefully what I just told explains things better.

[Pete M]

did you test any of the items or just replace them?

[87MJTIM]

First things you should do is read through Cruiser54.com and perform most of the procedures.  At least, perform all steps necessary to get it running.

 

The stopping once you let off the gas may be the idle air control valve.  This is located on the throttle body.  It may not be opening properly.  Try cleaning it with Throttle Body cleaner before throwing more parts at it.

[cruiser54]

Tips 1 through 5 COMPLETELY. Do it yourself. www.cruiser54.com

[Eagle]

An internal combustion engine needs three things to run: fuel, air, and spark. If you know you have air and spark, the question is fuel. But if you were able to start it and drive it home, you have fuel.

 

I don't think your mechanic is qualified to work on your vehicle.

 

[cruiser54]

THIS^^. 

 

CRUISER'S MOSTLY RENIX TIPS

THROTTLE BODY AND IAC CLEANING

OCTOBER 30, 2015 SALAD 24 COMMENTS

Originally by TJWalker of CherokeeForum & JeepForum

The Idle Air Control (IAC) is mounted on the back of the throttle body (front for ’87-’90).

The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is retracted, the air control passage flows more air which raises the idle speed. When the valve plunger is extended, the air control passage flows less air which lowers the idle speed.

Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea. This should be part of a normal tune-up procedure and whenever idle/stalling issues are present.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

1. Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a Torx driver (2 bolts; one can be kind of hard to get to). On ’91 and later, it may be easier to just remove the whole throttle body. Be sure to use a new throttle body to manifold gasket when reinstalling.
2. “Gently” wiggle out the IAC from the throttle body. Gasket/O-ring on the IAC can be re-used if it is not damaged
3. Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and oxygen sensors. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
4. Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner.
5. It is also a good idea to clean the entire throttle body bore itself, the butterfly valve inside of the throttle body and it’s edges, and all associated linkage as long as you have things disassembled.

Revised 1-31-2016