1998 4.0L wants to die on freeway

I have a 1998 Cherokee Classic 4.0L. A couple of months ago, while driving on the freeway at about 65 MPH it started to bog down on me. If I let off the gas, it would run OK, but the second I started to hit the gas again, it would try to die and act like it was vapor locking. It seems to be worse when I go up a hill, and especially if I am pulling a trailer. If I pull over for a few minutes and turn the engine off, it corrects the problem for awhile, but then will start again. This problem also seems to happen after I have driven the Jeep for more than a couple of hours. I have read the the CPS could cause this but it seems as though if the CPS is going out that the Jeep will actually die while driving, where mine keeps running. Any ideas of what this might be?

I have a 1998 Cherokee Classic 4.0L. A couple of months ago, while driving on the freeway at about 65 MPH it started to bog down on me. If I let off the gas, it would run OK, but the second I started to hit the gas again, it would try to die and act like it was vapor locking. It seems to be worse when I go up a hill, and especially if I am pulling a trailer. If I pull over for a few minutes and turn the engine off, it corrects the problem for awhile, but then will start again. This problem also seems to happen after I have driven the Jeep for more than a couple of hours. I have read the the CPS could cause this but it seems as though if the CPS is going out that the Jeep will actually die while driving, where mine keeps running. Any ideas of what this might be?

HI HAVE SOMEONE PUT A FUEL GAUGE ON IT. WIFES CHEROKEE ACTED LIKE THAT. PUT GAUGE ON IT SHOWED 38LBS. AT IDLE, CRACKED THROTTLE QUICKLY. IT DROPPED TO 21 LBS. IT RAN GOOD EXCEPT WHEN UNDER LOAD . HAVE PICTURES IF INTERESTED OF REMOVAL, AND INSTALL DALE jeepman600@sbcglobal.net :icon16: :disappoin

I have a 1998 Cherokee Classic 4.0L. A couple of months ago, while driving on the freeway at about 65 MPH it started to bog down on me. If I let off the gas, it would run OK, but the second I started to hit the gas again, it would try to die and act like it was vapor locking. It seems to be worse when I go up a hill, and especially if I am pulling a trailer. If I pull over for a few minutes and turn the engine off, it corrects the problem for awhile, but then will start again. This problem also seems to happen after I have driven the Jeep for more than a couple of hours. I have read the the CPS could cause this but it seems as though if the CPS is going out that the Jeep will actually die while driving, where mine keeps running. Any ideas of what this might be?

I would do a crank position sensor (CPS), they are not expensive. Because it is located on the automatic transmission, apparently the wires connecting it rub through and short intermittently when the car is bouncing along on the highway. The Jeep dealers do a lot of these on that year. As far as the fuel is concerned, checking pressure won't hurt but requires a special T and gage setup. I would change the CPS anyway because it can leave you stranded.

The symptoms you describe fit exactly a problem I had with an 83 Olds 88. The cause was water in the gas tank. It would slowly accumulate in the gas line resulting in the gradual loss of power and finally stalling. After sitting awhile, the water would return to the tank, replaced by gas resulting in it running well again for awhile before repeating. Might be worth a look.

I will look at the water in fuel possibility. I was speaking with a mechanic yesterday and he told me that if the CPS was going bad the check engine light would surely be on, has anyone experienced their CPS going bad with no check engine light on?

Yes a crank sensor can go bad without setting a code. But don't believe that is your problem. Thge crank sensor isn't going to change under a load. It is doing the same job the whole time. Now if it shut down and then crank back up after cool or something like that I would think crank sensor. In your case I think of fuel pressure being low. Not able to keep up with Highway deman. The Tps maybe but there again I would think it could act up at other times too.

Hmm, well I have tested the fuel pressure and it is great all the way to the rail, so I guess I will keep looking. Has anyone had problems with this engine with vapor locking?

Sorry to re-start this thread, but...
I started to have the same issues with my 97' Cherk.
It happened 5 months ago when I was driving home from about 150 miles away ( freeway speed 75+:evillol:). It started to stall then quit alltoghther...I could shift it into neutral and restart it right away but then give her a little throttle and sputter...sputter..die. Restart, repeat......I pulled off at the next exit and filled the tank with premium hoping it was just bad gas or water build-up. got home drained the tank refilled with MORE premium and she ran fine. I have not had any problems since (11000 miles) UNTIL NOW...
About 2 months ago I got promoted to a regional position and began to travel 250+ miles once a week. Now it is acting up again on these trips. I get to freeway speed and attempt to pass/ downshift and she just loses power altoghther, Not die, (she idles like a champ regardless) just loses power. If I release the throttle and only give it enough to get up to 65 mph she runs fine. It wont happen on the trip to (around 110 miles)..Only coming home. Any ideas?
SIDE NOTE...On trips to and from my branch office (About 80 miles one way) I have no problems for the whole trip..BUT... I am stopped there long enough for the engine to cool off signifigantly. So it's possibly heat related...
Heres what I know so far...
1. The plugs are fine. No fouling or bad arc.
2. All cylinders are firing normally. Idles fine all the time
3. Fuel tank checks out O.K. No moisture.
4. No check engine lights or trouble codes with KO KO
5. Cruise control DOES NOT FUNCTION. the light comes on on the dash but it won't hold speed.
I am stumped. I LOVE this damn thing to get rid of her but I don't want to be stranded 100+ miles from home either.

I had thi same problem with a ford mustang a few years back and ended up the the Cat convertr was blocked

I had that same exact problem with my 89 cherokee. I spent weeks tryin to figure out what was wrong.come to find out i had a lil plug unplugged from the fuel resistor (its the little white ceramic box screwed on to the driver side fender) i would check that before nething.

Sorry to restart this old thread but I couldnt help but notice there was never a solution to this problem. It would great to know what the fix was because im having the exact same problem. thanks.

First thing I would do is give it a massive dose of "dry gas".... a fuel additive that will aid in removing water from the gas tank (it actually helps to more fully homogenize the water with the fuel). I had something like this in my XJ and water in the gas is what it turned out to be.

If you've never had a professional intake tract serving done (cleaning injectors and upper intake tract) then drop $75 and have it done.... the improvements can be amazing. Most fuel injector cleaners you dump into the tank are a waste of money, IMHO...the exception being Chevron's Techron. But none of them will get the injectors as clean as a pro job can.

mike

Thanks for the help sector95... I myself think its the fuel pump or filter. So in the morning I have plans to drop the tank and change the pump. Ill post the details if it was the problem or not.

Experience similiar problem with my '97 Cherokee. Is it sputtering and back firing. If so check your exhaust manifold for a leak and catalyctic converter for clogging.

This is a crazy, disjointed thread. No one has indicated what they have found with their problem so other can benefit from your solution. Please try any report back so other can benefit and maybe you can benefit also.

Thanks and best regards....

This is a crazy, disjointed thread. No one has indicated what they have found with their problem so other can benefit from your solution. Please try any report back so other can benefit and maybe you can benefit also.

Thanks and best regards....
I am currently going through the same problem with my '87, It has 224K miles on it and I have never had this issue before. I have purchased a pump and plan to change it within the next week or so I will let you know what I find out. I also plan to replace the filter at the same time.

This is a crazy, disjointed thread. No one has indicated what they have found with their problem so other can benefit from your solution. Please try any report back so other can benefit and maybe you can benefit also.

Thanks and best regards....
Actually, I reported my solution to this in a thread I started a little while ago... http://www.automotiveforums.com/vbulletin/showthread.php?t=708327

^#*!@%!%#&*()!!!!! It turns out that the headers I put on were contacting the wires to the ( crankshaft position sensor ) CPS. Melted right through the loom and down to the wire about 1 1/2" long where it was hitting the 'heat'.

I guess the CPS was grounding out and causing the PCM to fail-safe itself.

WHAT A PITA that thing is to get out!

I'll not have those troubles again though. After getting the blasted thing out, I could see the extent of the damage and decided to try to fix it rather than spend the cool C-note. So I broke out the soldering iron and went at it making sure to cut out any corroded areas out of each lead. Some shrink-wrap, elec-tape, and a new stretch of loom, (<-is that what it's called?), along with a resistance (ohm) test (should read ifinite @ a 1K-10K setting for my year-'98 ), and I felt good enough to give it a try...

But how to get this *&&$^# thing back in there?! I came across a genious idea somebody posted.

Basically this: I took the dremel tool and a cutoff wheel to the mounting holes and made nothches out of them instead so I won't have to take the bolts all the way out again. I then carefully threaded the bolts back in a little and [I]slid the CPS back on. Tightened it up with my trusty 3/8's ratchet-10"extension-wobble-10"w/wobble extension-11mm socket.

(BTW- disconnecting the front sway bar and jacking the front drivers side way-up gave me just enough room to not have to touch any other bolts to reach the CPS and it's horrible placement!)

Well, all done! Thanks for all the help guys!~

Sh!t! I forgot to ziptie the wires! lol Anyway, she's running great with no codes! Gotta go!

Well, there ya go! CPS for me...

Its been a month but I finally got the pump in and everything is running great! The new pump is so quiet I hardly notice it and I seem to have a boost in Horse Power! I replaced the fuel pump, the sieve and the filter, also all the rubber fuel lines at the tank. Good luck to the rest of you!

OH Sh*T!!! Thanks Bro!!! We actually have an answer to this mysterious enigma... Let it be Known that it is NOT always the CPS! Thanks for the knowledge friend!