Can you help this lady?

Just received this email by an unknown woman from another state that sounds desperate to keep her XJ. Please have a read and tell me what you think as a lot of things like the CPS have been changed already that I thought would cause it. I'll try and find out the age but it will be an 94 or later model as we don't have anything else here in Oz. I should get her to read the codes too if it is a pre 97.

Hi,

I don't know if you can or even if you are interested in helping us but at the moment I look like I may be about to loose my beloved Jeep Cherokee. We have what appears to be an electrical problem with the Jeep and it keeps coughing and stopping. We have had it at a local garage for about two and a half weeks and the problem still exists. We live approximately 3 hours away from a Jeep dealer ( in Canberra) and no-one is able to help us by phone (or won't). I am writing in desperation as my husband says we should just trade it in and get a new car.... not a Jeep.

So far we have replaced all spark plugs, spark plug leads, fuel filter, crank angle sensor and coil (with a second hand one). The battery tests OK. The problem is intermittent which is making it hard to find. It will miss and occasionally stop. When it stops, it takes usually only a few minutes and it will start again. My husband has tested it somehow by removing a lead and checking for spark and sometimes there is a spark and sometimes not.

I don't know anything about cars so I don't know if I'm giving you much valuable info or not but I am desperate to keep my Jeep. If you have any ideas of what it might be or something else to try I would appreciate your input. Thanks for your time.

Kelly Row

I had a problem real similar to this once and found out that the plug going in to the coil had lost its rubber seal allowing the connector to bounce around cutting off spark. Have them start the jeep and jiggle that connectoer to see if it cuts in and out. It seems like it would have to be a loose connection somewhere.

TPS maybe?

Don't know if it has a fuel pump resistor; but that was the problem with my 89 - very intermittent when it warmed up - finally found it when I filled up with gas on a warm day - heat soak under the hood - and after trying another coil I jumped the resistor (on LF inner fender on 89) and problem solved.

Trouble shoot by checking schrader valve when problem occurs - no fuel could be fuel pump or maybe fuel pump relay??

There are pretty much only three sensors that can keep a jeep 4.0L from running. The crankshaft position senor, located on the bellhousing on the drivers side, the cam shaft position sensor, located in the distributor, and the MAP sensor, located on the firewall and has a tube running to the throttle body..

Other possibilities are the fuel pump ballast resistor, mounted on the drivers side fenderwell. It can be shorted around for test purposes.

The coil/iginition modules have been known to be the culprit, but much less likely.

i had a problem like that and all it was that the conetor on my map sencer was loose

This is a long shot but....what about the little rubber hose on the fuel pump assembly?Mine was sputtering/idling rough and hard to start.I replaced the little rubber hose and the inlet screen on the in-tank fuel pump and all problems went bye-bye.I actually need to do this on the wife's '91 as hers is displaying the same symptoms.That little rubber hose sometimes comes partially disconnected on one end and also deterriorates over time with the results being air sucked in at the fuel pump which,in turn,screws up the air/fuel mixture.Like I said,its probably a long shot but worth checking if for no other reason than to rule it out in the troubleshooting process. HTH
Jeff

Since they are getting intermitent spark it is obveously an ignition problem. When diagnosing problems I NEVER use second hand parts. I would say try a new coil or check the plug like mentioned.

Just out of curiosity, as this is an Australian model... Is it diesel or gas? I'm assuming gas since they mention spark plugs and testing for spark, but it might not hurt to clarify.

Not A Lot To Go W/ But How About The Sending Unit In The Gas Tank!
(coughing And Spitting)

It would help to know what year this is but I'll take a shot. Check the fuelp pump relay and the auto shutdown relay try swapping them with any of the othjer relays that look the same (for testing purposes) next try jumping the ground wire for the NSS switch and see if the problem goes away.

Point her to this web site so we can do it first hand...more or less..

By all means, try to find out what year. However, if they are certain that the spark is intermittant, that rules out fuel pump issues, as well as the MAP snsor. There is a possibility that the new CPS is bad -- they can be tested with a multi-meter, although that would not show up an intermittant fault. (Don't know if CPSs do intermittant faults, though -- usually they just get too weak to send a reliable signal.) The other likely suspect, assuming we can trust the gal's husband to reliably zero in on intermittant spark, is the aforementioned camshaft position sensor in the distributor.

mmarriottxj said:

I had a problem real similar to this once and found out that the plug going in to the coil had lost its rubber seal allowing the connector to bounce around cutting off spark. Have them start the jeep and jiggle that connectoer to see if it cuts in and out. It seems like it would have to be a loose connection somewhere.

Click to expand...

I had the same problem with mine. It would cut out occasionally but after a while it would start again. Ended up being the wire going into the back of the coil had a short and would sometimes work and other times it wouldnt. I would also check the ballast resistor on the fender as well.

AARON

Thanks guys for all the responses. I will give her the link to this forum so she can see all the great ideas that you have come up with. The only other thing I thought of was a loose ground somewhere between the battery and body, body and block and most likely in this case the body to ECU. I have heard this last one can make similar symptoms.

If the symptoms are indeed intermittant no spark, it could also be the coil or the ignition module. Again, knowing the year would help. On the Renix models that I'm most familiar with, the coil sits on top of the ignition module and the whole assembly is bolted to the right side inner fender (I was going to say "passenger side," but I realized that would be counter-intuitive for you lads and lassies down under). There is a procedure to do a crude go-nogo test on the Renix ignition module (checking for internal shorts, basically) using a multi-meter. This test is NOT in the factory service manual, I found it either Haynes or Chiltons. I don't know if the same or similar information would apply to the HO years.