mrobers

Hi guys! My first post on the Cherokee-forum

Short intro : my wife and I live in the Netherlands and love USA cars. We currently own the cars seen in my signature. Before my current daily - a Chevy Avalanche - I drove 3 years in a Grand Cherokee 5.2 and another 3 years in a Grand Cherokee 5.9. Some of my offroad-friends (www.chaosboyz.nl) drive CJ7's and because of my soft spot for Jeeps, I recently bought a '90 XJ for my wife for the winter. The Roadster and Corvette just don't move with snow

Ok, on topic! When I bought the XJ, the engine had a hunting idle and stutters badly (and I mean BADLY) during driving. I thought it could be the IAC so didn't mind buying it. You can barely drive it; the engine bucks while cruising and when under load, you can feel something like a misfire. So I went ahead and read a lot of stories on the forum and decided to replace the following :

• TPS
• MAP-sensor (including cleaning the vacuum hose)
• CPS
• Fuel filter
• Air filter
• Spark-plugs and cables
• Rotor and cap
• Measured engine temperature sensor
• Cleaned the IAC
• Seafoam through brake vacuum hose
• Flashlube injector cleaner in fueltank
• Reset ECU (disconnected battery)
• Checked for vacuum-leaks using brake-cleaner

After all of this the problem stays. I don't want to drive the car because I'm afraid I'll damage something. The odometer shows 273.000km but the XJ only drove 3000km in the last two-and-a-halve years.

I also checked for changes in idle by removing the injector-connectors one by one and all of them resulted in changes in the idle so it looks like every cylinder is firing. The old sparkplugs looked nice, a bit greyish in color.

I don't know what to do next. What else can I check or replace? Please help me in the right direction...

Here's a picture of my XJ (a bit misty during the photo) :

VTJeep

Hey man, welcome! Nice lookin xj ya got there. I like the side markers over wheels. As for issue, it looks like you've been pretty thorough, but the two things I didn't see was the o2 sensors and you said the fuel filter was changed; then the tank was dropped and inspected for crud, right? My 99's pump/filter assembly is in tank, I assume yours is same. IAC issues are usually associated with high idle issues. When replacing parts, in my experience, using quality, oem parts is the way to go. Unless upgrading with high quality parts, i.e. MSD ignition system. Good luck.

chill

A couple more things to check. crank sensor. fuel injectors.

mrobers

Thats a fast reply :-)

I did think about the O2 sensor but didn't have one laying around besides a new one from a Grand Cherokee but that one has 4 wires instead of 3 (if I only knew if you can connect that one?). I did remove the O2 sensor and cleaned the connector but I dont know how to test it so I just put it back.

Could this be a symptom of a bad O2 sensor? How can I verify that; can I disconnect it and take her for a drive?

Btw, I ordered all parts through Rockauto because they can ship to the Netherlands (fast)

mrobers

I replaced the crankshaft positin sensor with a new one from Rockauto as you can see in the list in my first post.

I also checked the injectors by disconnecting their connector with the engine running and all of them result in a change in idle so I guess they all do work. I can not check fuel pressure because my gauge doesn't have the right adapter for the testport on the fuelrail.

Is it correct I can not read error codes on my 90?

VTJeep

I understand about using who you can to get parts. Rockauto is pretty good, it seems. There may be more than one o2 sensor in exhaust. I only have my 99 to reference, so it's only so helpful.. But go over your exhaust system thuroughly. If you can get to a garage with a code reader, depending on quality of code reader and person oporating it, you should be able to at least get basic codes that have been storred in there, to actually looking at different sensors and seeing how acuratley they are reading. My cheap replacement TPS was only reading 2-3 percent open even when at full throttle. Swapped it for a good one and it was fixed.

Edit- you have a 90.. So I THINK you are odb1, so you can still pull some info??? Idk for sure..

chill

check the distributor, worn shaft. seen high speed running problems from this. actually check resistance on plug wires. new don't always mean good. how's the spark look?

cruiser54

If it's a 90, I assume it has the Renix fuel injection like our XJs did in 1990?
If so, you can tell becuase the intake boot is screwed on to the throttle body with 3 screws. Any photos of the engine?

mrobers

Yes, that is correct! It has 3 screws and the ECU underneath the dash has Renix written on it. Any known issues with that fuel injection?

I remember some play on the rotor axle but dont remember how much. I can check that; how much is normal?

Can I disconnect the O2 sensor and testdrive to see any difference?

cruiser54

Yes on the O2 sensor.

Please perform the following ground refreshing first off. Super important on your REnix. Do the upgrades if you can.
Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011
eshing procedure first off. Super important as explained in the instructions.

evilxj85

Check temp seers on motor.

mrobers

I did and it seemed OK according to the manual and everything I found on the forum.

I also removed the groundcable to the dipstick, cleaned everything up and re-attached. No change.

I finally brought the XJ to a friend of mine who is a mechanic and he is going to have a look for me. He just emailed me that he measured the CO from the exhaust and it fluctuates between 0.92 and 1.08 (should read between 0.97 and 1.03). So that indicates the O2 sensor isn't working correctly. But I can't imagine a bad O2 sensor could cause this bucking. It's nearly undrivable!

cruiser54

Do the complete ground refreshing before you do anything else.

big sam

HI mrobers

Very nice xj you have there. Please keep as posted to what the problem was as I have the same problem on my 98 xj and can't get is sorted out yet.

Best of Luck!!

evilxj85

a bad o2 will make it run bad.