Renix Guys...Long Post

[19864cyl]

I would suggest checking voltages, starting at the battery (check the battery clamps and posts, are they clean and tight).

With the vehicle running, stress test all the under the hood wires, too see if moving them causes any problems. You need to dig up an FSM for troubleshooting the 4 cylinder. Very few of us here have a 4 banger, and that year was a transition year, throttle body injector, with a bunch of special valves, that less than a handful of XJs here have. Also check for any call backs TSBs I think they call them, that might be related to your problem.

There maybe an idle reset procedure in the throttle body version that is not resetting a valve properly. The 87-90 Renix 4.0 l, needs 6-7 seconds of off time to reset, something called a B+ relay is involved, IIRC.

Even though it is a single fuel injector, throttle body injection (that is what you have right?), I would still look for a leaky injector partially floodding the engine on start up? Aslo look into those other valves the 2.5 L throttle body system used.

Search for threads here about the "throttle body injection" (use as key words in google with , or search here) for the other guy(s?) that has one of these beasts still running! And PM him to join us in this thread.

what do you mean by stress test? what is an idle reset? why would it flood it on start up? but on the initial start up it wont flood it? and sending other 2.5 guys pms is a great idea, thanks.

 

[stephenspann27]

Some guys are saying they are rare.. but if you could find someone else who owns one.. or find one in a J-yard and do a side by side comparison.... maybe grab the thorttle body from one in a j-yard..

 

[stephenspann27]

Also.. if you are using a haynes or chilton.. find you a FSM somewhere...

 

[mnaemark]

I have a 2.5 in the yard. sometimes pictures help more than words. If you need a pic of anything lemme know

 

[Ecomike]

so wait, there is suppposed to be a ground wire going from the negative batt terminal to the dipstick tube?

YES!

 

[Ecomike]

I dont think its heat soak because it dosent have to be hot for it to do it.

Sound conclusion, I agree. That leaves a fuel injector that is sticking and leaking fuel as a strong possibility. Should be easy to test.

 

[Ecomike]

what do you mean by stress test? what is an idle reset? why would it flood it on start up? but on the initial start up it wont flood it? and sending other 2.5 guys pms is a great idea, thanks.

Stress, as in wiggle, a shake the wiring harnesses.

The IAC (I think you have one of sorts like the Fuel Injected, multiport 4.0s), Idle Air controller, it's opening is reset by a time delay relay that delays power down of the ECU and IAC so it can reset the start up idle air possition of the IAC. Any failure in that circuit can cause restart problems. But yours sounds more like a leaky fuel injector based on the timing, as the leaked fuel will evaporate in 1 hour, and wont care if the engine is hot or cold on restart, only if the fuel dump is fresh and still there.

 

[Ecomike]

Some guys are saying they are rare.. but if you could find someone else who owns one.. or find one in a J-yard and do a side by side comparison.... maybe grab the thorttle body from one in a j-yard..

The 2.5s are rare, but surviving throttle body injected 86 2.5s are extremely rare.

 

[Ecomike]

what do you mean by stress test? what is an idle reset? why would it flood it on start up? but on the initial start up it wont flood it? and sending other 2.5 guys pms is a great idea, thanks.

PM 5-90, he might might be able to direct you to his yahoo site, for access to an out of print FSM on the 86.

And check this dealer site out:

http://oljeep.com/JeepEngines.pdf

 

[MikeESoc2]

I don't have an '86 4-cylinder but I do maintain a couple of XJ's and a ZJ in the family (between the wife and kids and me)... maybe my experiences with this will help somehow:

re:
"... 2. It smells like it is running rich
3. It has a ROUGH idle, but sometimes it will idle good for a few seconds then back to the rough idle. ..."
- that sounds A LOT like the cracked exhaust manifold on my son's '99XJ 4.0L (which was fixed only by me changing-out the cracked manifold for a new one);

re:
"... 1. The idle is low
5. It bogs, misses, skips, acts like it is starved for fuel, or like the coil stops working. Then a couple of mins later it will run decently.
7. Its likes to miss, skip, bog, under really light throttle when im just cruising. ..."
- that is somewhat what was happening with the wife's '97ZJ 4.0L last year (which included the bad behavior of sometime totally cutting-out while cruising on the highway) ... my first attempt to fix included changing all the possible usual suspects (especially since the OBD-2 code was indicating intermittent ignition failure) ... first changed: ignition coil + spark plugs + ignition wires and then moved onto changing the fuel-pump and the crank position sensor and then the idle-air bypass valve... after I ran out of the usual stuff to change (including running a couple of additional ground cables to the engine) I then hit-n-miss played-around with the connectors for the computer (wrapped double wire-ties around the ECU and the 3 connectors to make sure the connectors were stable into the ECU) and then (long-story-short) after I removed the ECU and I got the computer back from being re-manufactured (~ 6 months ago) the wife's '97ZJ 4.0L has been running real nice since (hopefully will stay that way)

Also:
back a few years ago after I had replaced the throttle-body on my '87 XJ 4.0 (auto-trans) I didn't re-adjust the TPS correctly... WOW... bad driveability including the auto-trans would all of a sudden decide to down-shift while cruising along ... after re-adjusting the TPS correctly (which I did via trial-and-error) the '87XJ was back to nice behavior.

 

[stephenspann27]

I don't know about out of place, but that's got to be about the cleanest engine compartment I've seen in a long time.

All dressed up and no where to go.....

(Sorry I couldn't resist...)

 

[19864cyl]

I have a 2.5 in the yard. sometimes pictures help more than words. If you need a pic of anything lemme know

Thanks man that could help a ton

 

[19864cyl]

YES!

I dont have one, guess Ill do that today.

 

[19864cyl]

Stress, as in wiggle, a shake the wiring harnesses.

The IAC (I think you have one of sorts like the Fuel Injected, multiport 4.0s), Idle Air controller, it's opening is reset by a time delay relay that delays power down of the ECU and IAC so it can reset the start up idle air possition of the IAC. Any failure in that circuit can cause restart problems. But yours sounds more like a leaky fuel injector based on the timing, as the leaked fuel will evaporate in 1 hour, and wont care if the engine is hot or cold on restart, only if the fuel dump is fresh and still there.

ahh how do i test to see if its leaking? just remove the breather and look?

 

[19864cyl]

PM 5-90, he might might be able to direct you to his yahoo site, for access to an out of print FSM on the 86.

And check this dealer site out:

http://oljeep.com/JeepEngines.pdf

great site, thanks man

 

[19864cyl]

I don't have an '86 4-cylinder but I do maintain a couple of XJ's and a ZJ in the family (between the wife and kids and me)... maybe my experiences with this will help somehow:

re:
"... 2. It smells like it is running rich
3. It has a ROUGH idle, but sometimes it will idle good for a few seconds then back to the rough idle. ..."
- that sounds A LOT like the cracked exhaust manifold on my son's '99XJ 4.0L (which was fixed only by me changing-out the cracked manifold for a new one);

re:
"... 1. The idle is low
5. It bogs, misses, skips, acts like it is starved for fuel, or like the coil stops working. Then a couple of mins later it will run decently.
7. Its likes to miss, skip, bog, under really light throttle when im just cruising. ..."
- that is somewhat what was happening with the wife's '97ZJ 4.0L last year (which included the bad behavior of sometime totally cutting-out while cruising on the highway) ... my first attempt to fix included changing all the possible usual suspects (especially since the OBD-2 code was indicating intermittent ignition failure) ... first changed: ignition coil + spark plugs + ignition wires and then moved onto changing the fuel-pump and the crank position sensor and then the idle-air bypass valve... after I ran out of the usual stuff to change (including running a couple of additional ground cables to the engine) I then hit-n-miss played-around with the connectors for the computer (wrapped double wire-ties around the ECU and the 3 connectors to make sure the connectors were stable into the ECU) and then (long-story-short) after I removed the ECU and I got the computer back from being re-manufactured (~ 6 months ago) the wife's '97ZJ 4.0L has been running real nice since (hopefully will stay that way)

Also:
back a few years ago after I had replaced the throttle-body on my '87 XJ 4.0 (auto-trans) I didn't re-adjust the TPS correctly... WOW... bad driveability including the auto-trans would all of a sudden decide to down-shift while cruising along ... after re-adjusting the TPS correctly (which I did via trial-and-error) the '87XJ was back to nice behavior.

great ideas. i think it could be that my tps is out of adjustment

 

[Ecomike]

ahh how do i test to see if its leaking? just remove the breather and look?

Fuel pump runs for 7 seconds to pressure up the line when you switch from off to run (no need to start) on the 4.0 Renix, so it might be the same on yours (probably is as that is somewhat standard, universal on fuel injection), so get things to where you can see the injector tip and have someone else turn the ignition to on, not start, and watch for a drip. If you can rig it some how, it would be nice to be able to start it, run it, turn it off and be able to immediately look for temporary leaking at the injector tip after turning the engine off. I am not familiar enough with your layout to say how to do that hardware wise on the throttle body!

 

[19864cyl]

Fuel pump runs for 7 seconds to pressure up the line when you switch from off to run (no need to start) on the 4.0 Renix, so it might be the same on yours (probably is as that is somewhat standard, universal on fuel injection), so get things to where you can see the injector tip and have someone else turn the ignition to on, not start, and watch for a drip. If you can rig it some how, it would be nice to be able to start it, run it, turn it off and be able to immediately look for temporary leaking at the injector tip after turning the engine off. I am not familiar enough with your layout to say how to do that hardware wise on the throttle body!

thanks ill try that out.

 

[Matthew Currie]

I have a chilton book that has extensive troubleshooting and testing info for the 2.5 TBI system. You might want to see if you can find a copy somewhere. It includes testing flow charts for just about every component of the system. I would try scanning it and putting it on box. net or something, but the section is many pages long, and the print for the diagrams so fine I don't think I could get it into a reasonable sized file.

It is a Chilton guide to "Fuel Injection and Electronic Engine Controls - 1984-88", part # 7768. Probably out of print, but some library might have it.

http://openlibrary.org/b/OL2741584M..._injection_electronic_engine_controls_1984-88

If you end up just hopelessly stuck, PM me and I'll see if there is some way I can copy the pages and mail them to you.

 

[19864cyl]

I have a chilton book that has extensive troubleshooting and testing info for the 2.5 TBI system. You might want to see if you can find a copy somewhere. It includes testing flow charts for just about every component of the system. I would try scanning it and putting it on box. net or something, but the section is many pages long, and the print for the diagrams so fine I don't think I could get it into a reasonable sized file.

It is a Chilton guide to "Fuel Injection and Electronic Engine Controls - 1984-88", part # 7768. Probably out of print, but some library might have it.

http://openlibrary.org/b/OL2741584M..._injection_electronic_engine_controls_1984-88

If you end up just hopelessly stuck, PM me and I'll see if there is some way I can copy the pages and mail them to you.

I tried to find it but had no luck. If i cant figure it out soon Ill send you a pm, hopefully it wont come to that though haha. Thank you so much man