Help: 89XJ stalling

(Did some searching but haven't yet found anything that is similar to my symptoms)

I've had my 89 XJ LTD 2 Door, I6, Selectrack (all original) since new. In all the years I've owned it, it's never stalled. In the past week or so it's stalled several times, always just off idle and when the engine is relatively cold, i.e. within minutes of a cold start. The stall is intermittent, i.e. it doesn't always happen when cold but when it does happen, it seems to occur several times in a row (as in: sometimes stalls when pulling up to a stop-sign, re-starts no problem but then stalls again at the next stop-sign, restarts no problem, etc.). Once it gets warmed up it doesn't seem to be an issue (so far). I've taken a rudimentary look under the hood checking for loose hoses and connections as well as shaking wire looms wherever I could but can't find any obvious problems. I've been driving back and forth to the mountains all winter and purposely keeping my tank only half full (thinking there's no sense dragging a full tank up and down the mountain) and thought maybe my problem was moisture in the fuel but I've since added a couple of bottles of the fuel conditioner that's supposed to dry out the fuel but it doesn't seem to have done anything.

I know my problem could be any of a number of things but I'm wondering if there are any 'typical' known XJ trouble points that might cause this kind of behaviour.

I think my 89 has a Renix FI system, is there such a thing as a code reader for something so old?

Thanks for any advice.

Yes, you have a Renix, yes there's code readers for stuff that old, unfortunately the Renix system doesn't store codes, so you're kinda SOL there...

1) When it isn't stalling, does it idle at around 800 rpms?
2) When it stalls, does it quit like you turned off the key or does it sputter a bit?
3) What is your power like?
4) What color is the inside of your exhaust pipe?
5) If you turn on the heater, does it go only to the defrosters?

As a rule, I run a can of BG44K through every vehicle I own every 10k miles. It will help clean the fuel system including injectors and on an old vehicle, it normally helps power and mileage. It isn't a bad idea and may help.

JeepNoob said:

Yes, you have a Renix, yes there's code readers for stuff that old, unfortunately the Renix system doesn't store codes, so you're kinda SOL there...

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Thanks JN.

old_man said:

1) When it isn't stalling, does it idle at around 800 rpms?
2) When it stalls, does it quit like you turned off the key or does it sputter a bit?
3) What is your power like?
4) What color is the inside of your exhaust pipe?
5) If you turn on the heater, does it go only to the defrosters?

As a rule, I run a can of BG44K through every vehicle I own every 10k miles. It will help clean the fuel system including injectors and on an old vehicle, it normally helps power and mileage. It isn't a bad idea and may help.

Click to expand...

Thanks for your note Old Man.

1/2) Seems to idle rock solid then just dies. Occasionally, I'm stopped and it's idling fine and when I just press the gas, it drops out but will come back up without stalling. I've never had a problem with the idle surging as mentioned in several other similar posts.

3) Engine runs smooth and no problems with power and otherwise running normally except for the off-idle intermittent stalling problem.

4) I'll need to take a look a the tail pipe. I don't expect it to be particularly carboned up. The only driving I do is on the highway, typically at about 110kmh (~70 mph) typically cruising in OD, except for getting to and from the highway which takes about 20 minutes of stop and go.

5) heater works normally in all settings, or more accurately works as it always has. There's pretty much only hot or cold setting with a very small range in between - basically the center of lever setting - but it's been that way since the day I drove it off the lot.

I typically run a can of injector cleaner through it a couple of times a year.

Just a little more information: It stalled on me several times yesterday in the morning and later in the day after sitting for several hours. Today I drove about 160km and it didn't stall or hesitate even once.

Forgot to mention: original mileage is about 220k kms (120k miles)

If I had to hazard a guess, I would say either MAP or more likely the throttle position sensor. You can test both with a voltmeter.

I'm with old man. Does it have an Intake temp sensor? Not real deep into a renix here but it couldn't hurt to check it too.


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Thanks for the suggestions guys. I'm going to try to spent some time inspecting and cleaning up connections tomorrow.

PS: Drove the XJ several times today from cold starts and didn't have any problems.

PSS: I'm not 100% sure but I think the problem may only occur at low gas tank levels i.e. at or near the low fuel warning light coming on (I haven't had a stall since I put a half a tank of gas in yesterday). I'll have to monitor a bit to see if this is accurate.

XJBucko said:

Thanks for the suggestions guys. I'm going to try to spent some time inspecting and cleaning up connections tomorrow.

PS: Drove the XJ several times today from cold starts and didn't have any problems.

PSS: I'm not 100% sure but I think the problem may only occur at low gas tank levels i.e. at or near the low fuel warning light coming on (I haven't had a stall since I put a half a tank of gas in yesterday). I'll have to monitor a bit to see if this is accurate.

Click to expand...

Can it be something to do with the evaporative emissions? Only with little fuel in the tank? Or did the renix not have evap? If it did I'd try unplugging the evap solenoid and seeing if it still tries to die. If the purge solenoid sticks its effectively a vacuum leak.


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Renix years have the fuel pump in the tank. Over time the short piece of hose in the tank from the pump to the outlet will degrade/crack. You end up losing fuel pressure, especially when the tank is low.

A few things pop to mind. You said it happens mostly on a cold motor, maybe a lazy 02 sensor. I've run them well over 150,000 miles, Jeep recommends swapping it out at a round 90,000. Ask EcoMike what he thinks.

CPS usually screws up hot, not cold. But stalling at idle can be a CPS slowly failing. Might want to check the very rear of the valve cover gasket, with a flashlight. Oil soaked CPS can get unpredictable.

The CPS wiring has been known to cook on the exhaust manifold.

Stalling while accelerating from a stop kind of has me stumped. The reverse, stalling while stopping, is a lot more common. Sticky IAC or EGR will do that.

Try this before blaming sensors which are known to have piss poor grounds.

Tips 1 through 5 in my signature.

I would think a bad TPS would cause the problem hot or cold, not 100% sure. The Temp issue has me thinking the O2 sensor is not hot enough at idle, thus a problem with the electric heater in the sensor or no power to it.... or the Intake temp sensor (dirty and fouled? but that can also cause idle speed issues).

The fuel tank pump hose issue makes some sense so far.

How well is the rig maintained? Plugs, wires, Cap, rotor, grounds and so on....???

Any other issues at all!!!!!!!! ?????

old_man said:

If I had to hazard a guess, I would say either MAP or more likely the throttle position sensor. You can test both with a voltmeter.

Click to expand...

I would agree, but the "only when its cold" makes me think maybe not.

Sounds like it gets hung up trying the switch from open loop to closed loop when it gets the gas and the O2 is still too cold. But many things can cause stalling on acceleration. The only when it is cold is a good clue!!!!

Hell being renix it could be a poor sensor ground thermal change...

Check the fuel pressure.

macgyver_7_6 said:

Check the fuel pressure.

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That would only be useful if done at the precise cold start moment that it dies, as it has no (fuel pressure) or other issues, according the OP, at any other times, yet. And even then the pressure would change on loss of vacuum tot the FPR as it dies. Not sure how useful that would be at this time?

Just grasping at straws. It's the scientific side of me...always have to eliminate the variables.
My old 86 idled fine, but under load it wouldn't allow me to go more than 50mph.
Never died, but it was a weak pump.
Thought you may uncover a clue by checking pressure at cold idle, operating temp, and while revving.
Call me crazy, but I've stumbled across intermittent issues in the past by getting desperate!
Good luck.

I had 70,000 miles on my 87 Waggy, 12 years or so before I stumbled on the real cause of its pisspoor no guts acceleration. It was not low compression like I feared.

It was a bent throttle body to gas pedal rod that changed the TPS to throttle plate opening ratio and the ECU was not smart enough to compensate on renix. I discovered it using my new to me MT-2500 snap-on scanner "brick" testing the TPS data, engine off from idle to WOT. the WOT was way off!!! The cause???? A bent 10 cent piece of metal rod.

Confirmed by comparing the rod to my 89 that ran perfectly.

Two minute bench vise fix.

Just updating this thread.....

Jeep has been running fine for the last 6 weeks or so with no stalling. The only thing I did was to add a bottle of fuel conditioner (specifically one that removes moisture) x two tanks of gas. Not sure if that resolved the problem or if I'm just on a temporary reprieve from some other problem.