Okay, I am new to this forum and I need to get an answer as soon as possible as this Jeep is going on a long trip next week.

I have a 1997 Jeep Cherokee Sport, 4.0 4WD. Only have had this about 6 months and I have fixed everything on it except one really annoying occurrence. Every so often the Jeep with just stammer, almost jump like it is going to die but keeps lunging on. Sometimes it will do it a couple times and keep on going, a few times it has been so bad that it would not go over 25 mph and just kept chugging on.

My thought is it ether a bad fuel filter or something in the gas tank. I plan on dropping the tank this Friday night and changing the filter and possibly other things while I'm in there, and also checking the inside of the tank. But I fear this may not be the issue and my daughter is having to drive this to a job some 18 hours away and I'm really worried about something going wrong.

Despite this problem the Jeep never gives me any trouble and runs incredibly well. I have already changed plugs, wires, cap, transmission fluid and filter, and recently had to replace the water pump.

This problem seems to come and go and it doesn't seem to matter how fast you are going. Also, if it gets bad, you can pull over and turn it off and let it sit for a minute and then it will fire up again and run like nothing happened.

I don't know a lot about Jeeps (like why you would put a fuel filter on top of the fuel tank) so any help is much appreciated. Hope someone gets back to me soon.

Thanks.

 

Welcome to the forum.

Your symptoms of intermittent stalling (not exactly now what stammer is could be several things. High on the list is a faulty CPS (crankshaft position sensor). It is notorious to give intermittent symptoms before it will eventually fail completely. You can to tests regarding it, however those are not always conclusive. At some point in the life of the 4.0 this CPS will fail, so it might be a good time to look into a new one. Try to get an OEM one, they are by far the most reliable.
A bad CAM sensor can also cause the symptoms, but is less common.

Often, an intermittent issue leans towards an electrical rather than mechanical cause.
Yes, intermittent could be a fuel delivery issue. I'd not per se drop the tank just yet(the fuel pump is an assembly in the 1997 that holds the filter, regulator and some other stuff, all in one). Because it is relatively easy, you could measure the fuel pressures you're having to see if they are within spec. Although the issue is intermittent, it wil give a general idea about the pressures you're having.

But my first thing would be the CPS.
See how you go, if you swap it out now for a good one, you still have time to check if the issue is ungoing or resolved (given the short timeframe we have....)

PS: If you put in a new rotor too, you have completed that part of the tune up

 

I had read something about the CPS somewhere else. Where is that located and is it an easy change?

My only other thought would be the catalytic converter being clogged.

I drove this this morning and on a 15 mile trip it started doing its thing, more like it is lunging, you give it the gas and instead of just taking off it lunges and falls back over and over. It doesn't die. My reasoning behind the gas is it acts like a car would when it has barely enough gas to keep it going to it just sort lunges with each drop it gets.

On my 15 miles trip back home it ran fine until I was about two blocks from home and it stuttered twice and that was it. As I said, there is no rhyme or reason to it.

The filter, as you said, is all one part. Looks like it runs about $200! Definitely an expensive replacement for something that may or may not be bad. But, I can't imagine this having ever been changed and wouldn't the filter needed to be swapped out after 17 years!

Thanks for your help.

 

The cps is located ton top of the transmission bell housing where the mitor and transmissionmeet toward the driver side. I heard it a pain but is do able with basic tools. I heard of people unbolting the transmission crossmember and lowering it down to gain a little more access to the cps. Good luck

 

Not per se. I'd hold off on the fuel pump for now.
verify fuel pressures with a gauge, to see of your baseline pressure is ok (since the issue is intermittent you likely won't catch an actual fuel pressure drop it when it is doing 'its thing' again)

The CPS is on top of the bell-housing. You will need some extensions to reach it, and those who've done it, are overall not of the opinion it was overly complex. Mine was replaced in the era when I was not doing my own repairs yet, so can't speak from personal experience.

 

Well, I changed the CPS ($87). Had a heck of a time getting to it. Had to remove the shifter cable assembly for more room and then had to buy a better swivel in order to get it off. I battled for a half an hour trying to get it off with 4 extensions and a cheap knuckle swivel and could not budge it. Went and spent $10 on a impact swivel and had it off in five minutes.

I really though the magnet on a the new CPS would be stronger than the one I took off the Jeep, but it wasn't any different. What goes bad in these things?

I drove the Jeep for about 60 miles today, it stammered once for a half a block in the first mile but didn't do it again the rest of the day. I went ahead and changed the coil on it and cleaned some connections, my daughter is driving it around now so I am hoping that one of these two things was the problem. If not, I may have to go back to taking the gas tank off and changing the pump and filter.

Thanks for your help.

 

hmm, not quite happy with the stumble for half a block.
What CPS did you get?

 

Sure sounds like fuel starvation to me.

Does it get worse climbing a fairly steep, long hill?

 

Well, my daughter has been driving it and it did it once to her. Seems to do it when you are driving 30 mpg or less, at least so far. Other than the fuel filter I really have no other ideas, there is no real reason behind when it does it, just occasionally whenever it feels like it. Not as bad as it was, but still there.

 

This MAY be an indication the fuel pump is getting weak, and on its way out.

 

So,again, what brand CPS? You REALLY want an OEM for this sensor.
fuel filters in your year is integrated, well attached, to the fuel pump assembly in the tank. Its more of a sock, so not an online type that the older XJ has. Fuel pump could be playing up, so get some fuel pressure readings. CAM sensor is another, but less common cause.

 

I ended up buying a fuel pump/regulator/strainer etc... It was actually easier to change this than the CPS, had the tank off in an hour, had it back together in another hour. Now that I have done it I think I could do the whole thing in less than an hour.

When I took the pump out the strainer was floating around in the tank. Not sure if it fell off when I took it out or it had been floating around in there the whole time. It was really dark, almost black, so I am hoping this was the problem.

Driven it 30 miles since the change and it has not done anything yet. So far so good. The only annoying thing is this is what I was going to do first but then opted for the CPS and then the coil. Could of saved myself some time and money if I had gone with my gut instinct. Oh well, at least all of this stuff is new now and hopefully I won't have to worry about it anymore.