There's a couple of sensors I would replace. The temperature sensor for the
computer, not the one for the gauge, and the ambient air sensor that's
screwed into the manifold. It's been my experience that as these sensors
age they vary on the side of reporting too cold of a value and your engine
runs rich. You could also have a vacuum leak somewhere. On a car almost 20
years old it may take you a while to isolate the problem. I had a 89 xj once
and it ran ok but when I replaced the o2 sensor it really made a difference.
The Crank Position Sensor normally causes hard or no starts as they go bad.
As Mike has replied clean and seal connections under the hood. Don't forget
the ground straps.

On the Renix systems the tester can only give real time readings and
since yours was not failing when they worked on it they didn't see anything
wrong.

JoBo

"NT" > wrote in message
...
> Hi:
>
> Update on my troubles...
>
> I finally got around to taking the truck into the dealer today. The
> Dealer ran all possible sensor tests and checked the fuel pressure and
> spark and couldn't find anything wrong. The problem is still there (as
> far as I know). The problem seems to happen when the engine is thoroughly
> warmed up; on the drive over this morning, I guess it didn't warm up
> enough as the problem wasn't there - but it was there on the weekend when
> I was out on the highway. The dealer assured me that they warmed the
> engine up thoroughly and still couldn't find any problems.
>
> Not sure what to try next. I'm a little leery about starting to replace
> sensors and the like when the analyzer showed nothing wrong. The Dealer
> suggested that it could be the CPS (which has never been replaced) but
> when checked it seemed to be working fine. If the CPS is being flakey -
> why wouldn't it have been apparent when the dealer warmed the engine up
> for the test? - Maybe it's a vibration thing?
>
> I've discovered a little more about the symptoms.......
>
> The engine idles fine and runs well at all speeds and acceleration rates
> when cold.
>
> Once warm (either that or it's a distance thing), there is significant
> stumbling (feels like all cylinders are cutting out not just one or two)
> on mild acceleration, although, if I hammer it down, there will only be
> slight stumbling and it will accelerate like normal. Even though slight
> accelerating will cause it to stumble heavily, I can very slowly bring it
> up to highway cruising speed and it will cruise just fine - but hit a
> slight hill and it starts to choke!
>
> Once this problem starts happening, the idle becomes very rough as well,
> but it doesn't stall (at least not yet), but it does sound as if it's not
> running on all cylinders.
>
> I wondered if it could be some moisture in the gas. I was low on gas so I
> added a half tank and poured in some injector cleaner that is also
> supposed to take moisture out of the gas and that didn't seem to make any
> difference.
>
> Anyone else have any comments or suggestions?
>
> Thanks.
> --
>
> "NT" > wrote in message
> ...
>>
>> Hi:
>>
>>
>>
>> I'm hoping some of you XJ fans can offer some suggestions on a problem
>> that just happened to me today for the first time.
>>
>>
>>
>> First of all, the specs: 1989 Cherokee LTD (XJ), inline 6 cylinder, 4
>> litre, with 150k Km's (ie: relatively low mileage, or more accurately
>> 'kilometerage' for the year).
>>
>>
>>
>> I drove to Costco this morning, about a 15 km drive. Everything was fine
>> on the drive there but when I started the truck up to come home (1/2 hour
>> later), it was idling roughly and would stumble quite a bit while driving
>> (but it didn't stall) - it felt like it wasn't running on all cylinders.
>> I did make it home where I did a thorough once over of under hood wires
>> and hoses and couldn't see any obvious problems.
>>
>>
>>
>> The last time I drove the jeep was about 3 weeks ago. It's rained a lot
>> since the so it could be that some water has got into the gas tank, but
>> I've lived here in Vancouver for over 20 years and the constant rain we
>> get for 9 months of the year has never been a problem before.
>>
>>
>>
>> My XJ has never failed to start since I purchased in new in 89, however
>> after it was a year old, it began to take a bit of cranking (say 20
>> seconds) to get it going. It's been that way ever since. I took it to
>> several dealers all of who said that a bit of cranking was normal. Since
>> it wasn't normal when the jeep was new, I've often wondered if the CPS
>> was faulty, but in all the reading that I've done, a faulty CPS seems to
>> manifest itself in intermittent start failures and I've never had a start
>> failure.
>>
>>
>>
>> Anyone have any suggestions on likely candidate for the source of my
>> trouble? Thanks for any advice.
>>
>>
>>
>> Regards,
>>
>> Dave
>>
>>
>> --
>>
>>
>>
>
>