I am going to be as descriptive as possible here. I've read a ton of posts on this website and others that 'kind of' describe my problem, but the descriptive abilities of the posting person make me question whether their problem is the same as mine.

So here goes...

When starting the cold engine (after sitting overnight, or sitting all day in the parking lot at work) my 1996 Cherokee Country starts up and the engine runs fine. After either 2 miles of driving at 50mph, or after about 5 minutes of idling the engine shuts off completely and dies. When the problem first started happening, all I had to do was crank it over repeatedly while waiting 30 seconds to a minute between attempts. Eventually the engine starts back up and the rest of the trip, no matter how far, I have no more problems. As time progressed (I lived with it for about a month) the time it took to start back up after cranking seemed to be longer.

What happens when it dies:

When the engine is about to die, I know it. The RPMs drop and the engine shutters and sputters like its running out of fuel. LIKE it's running out of fuel. Fuel level has no APPARENT effect on this phenomenon. The engine runs clean and smooth when it runs. It idles kinda crappy sometimes, but I think I've just got a vacuum leak somewhere or it may be the fact that its got 220,000 miles on it...but its like flipping a switch. It either runs fine, or its not running at all. I live 50 feet from the 50 mph highway that I take to work, and when I start the Jeep and let it idle for a minute I pull out of the parking lot and right on to the highway. I do this the same way every morning, consistently. I know that the Weigel's is 2 miles from my apartment, and once I reach the Weigel's, the Jeep starts to die. I can guarrantee it to happen at about that 2 mile mark every time.

What happens when it starts back up:

Sometimes, probably 2 out of 10 times, I can pump the gas pedal AS FAST AND DEEP as I can to keep the engine running. But the RPMs are so low while I'm doing this that the Tach doesn't even register and it seems as though its running on just a few cylinders when I'm doing this and the engine sounds like crap and the Jeep shakes like crazy. Keep in mind - I have to pump so hard and fast that my leg gets sore from the violent intensity required to keep it barely alive. If God is on my side that morning, I can do this for about a minute or two straight and eventually I can get it to rev back up and run smooth again. If that happens I may have to do it again on the way to work, but its much much easier and seems to not fight me so much. Usually if I win that battle, it doesn't act up again.

Most times, unfortunately, if I can't pump hard enough (because casually pumping the gas gets ZERO response) it will die in the same spot every time. If I just idle instead of drive, it dies consistently after a few minutes. Once it's dead, I coast onto a side street and begin trying to start it back up. I quit driving it months ago because I didn't want to get stranded and have to call someone or a tow truck, but so far it has always started back up after cranking over for some time. It has started to take longer to get it to start again, though.

What happens when it starts back up:

After cranking it repeatedly, enough times to start wearing down the battery and slowing the starter motor, the Jeep starts back up - enthusiastically. It then idles as if NOTHING happened...kinda reminds me of my kid when he does something wrong that he thinks he can get away with, "Did you just eat my M&Ms?" ... "No..(as he keeps drawing without batting an eye)" And once it starts, I usually have no problems with it, not even a sputter, until I let it sit for a whole workday or all night. Then its the same game all over again.

What I've tried so far:

Pretty much nothing. Its so mind boggling, I've only been able to think about it. Is it electrical? Is it fuel related? Its it a curse? I once had it shut off as I was going uphill, and I was stuck sitting uphill (engine above fuel tank...fuel pump fighting gravity) and it seemed to take so much longer to get a startup than usual.

What I've thought about:

I've read that the crankshaft position sensor could be bad or going bad. But if that's the case, then how can that explain the fact that the engine runs great and shuts off consistently at the same spot on the highway every time it happens?

I also thought that maybe it was a clogged fuel filter, but I doubt it because if the fuel filter was clogged then I would never get proper pressure and the engine would not run so smooth and nicely when it runs.

It could be that the first two miles of my trip is using the fuel that is still in the fuel lines from the night before, and once that fuel is used up it shuts down until the fuel pump starts to work properly. Which would explain the consistency, but doesn't explain why I can hear the fuel pump whirring every time I turn the key to "on" as I attempt to crank, nor does it explain why the engine runs smooth once it starts back up. Maybe the fuel pump is going bad but I can't offer any evidence of that.

Could it be my ignition system for some reason? I doubt that, too. Again, the engine timing is fine when it's running. It doesn't go through fuel at inconsistent rates (I always get between 17 and 19 mpg per tank) and my OBD II reads no codes. Ignition system is clean in my book, unless the distrubtor gets out of time/sync at that exact two mile mark and then gets realigned from repeated cranking....doubtful.

The only thing I can think of is an idea my fiance's great grampa gave me. He said the choke could be getting stuck and thats why it runs fine in the beginning but then I have to keep cranking and pumping the throttle to get it unstuck after it chokes itself out and dies. The problem is, it's MPI and doesn't have a carbuerator. Does it have an automatic choke? I feel dumb asking that because I've been elbow deep in the intake/ intake manifold before but it's been awhile. Could it be getting gunked up and stuck shut until it is somehow knocked loose and opened after shut-down and cranking? This makes sense to me but I'm not going to start buying parts and experimenting until a smarter person than me can give me more insight.

Thank you for any help and I apologize for the length of this post!

Chris

 

First off- I'm no expert, but I've been messing with cherokees for the last 3 years pretty intensively.

That being said, it sounds like something related to the warm-up cycle. The advice about the "choke" might not be that far off. The IAC (idle air control) is a small servo device that modulates airflow into the throttle body, mostly at idle but if it's getting stuck open that would cause issues. The throttle body will suffer from gunk build-up, particularly the small spaces around the IAC plunger. If you haven't done it lately, I'd say start by taking the throttle body off the intake manifold, remove the IAC and clean everything as best you can with throttle body cleaner. I use q-tips to get into the cracks where the IAC goes. There can be some serious gunk/varnish build-up in there. I'm pretty sure you can also test the IAC while you have it removed by plugging it into the harness and turning the key to On (not start) and it should move the plunger on the IAC, if not it should be replaced.

If that doesn't help, then you'll probably have to start diagnostics like testing other sensors with a DMM and checking fuel pressure.

 

PotatoWalker

Yeah I'm pretty sure you're right. Now that I think about it, I replaced an IAC for a friends girlfriend a few years ago on an Infinity J30. Front-wheel drive V6 cars are my least favorite for engine work because there was no friggin room to work with. I tore apart the entire intake region of that engine just to get to it. He was ready to drop a few hundred bucks on a new one but I cleaned it with meticulous detail and the car ran fine after. I think I'll try that and I'll get back at you in the next few days. If anyone else has had this happen to them please chime in.

What is the significance of "PotatoWalker" ? You just like 'taters??

 

Aside from the myriad of sensors that could be starting to fail, it could be your fuel pump. It may start strong, but after a couple of miles lose the ability to keep pressure, only to crank right up 10 seconds later.

It really sounds like fuel/air delivery rather than spark. Test sensors with a voltmeter & do a fuel pressure test. At the very least, press on the valve at the fuel rail to check pressure once it starts acting up & after it dies to see if fuel is being delivered. Most sensors aren't very expensive ($40), but the MAP is around $80, not including O2 sensors.

If you have to change the pump, pick up this stuff made to hold gaskets in place. It comes in a can like PVC glue. It's super tacky & you'll likely need it to hold the tank O-ring in place during installation, unless of course you decide to drop the tank.

Please keep your progress updated. I've battled a similar problem recently & I'd like to know the outcome.

 

It still could be your CPS. Check and see where the wires for it are ran, make sure they're not close to the exhaust manifold. Mine were ran beside the exhaust manifold and would go out after so many minutes up the road. Turns out once the manifold got hot enough it would start to heat the wire up very hot and it would malfunction and start to cut out until it would shut off completely. Give it a few seconds and it would crank right back up.

 

If the wires are too close, just cable tie them up out of the way.

 

hehe my dog's name is Potato, hence at least 3 times daily I am the Potatowalker.

and yea, some cars are a real pita to work on. Toyotas are all crammed together and if you don't have real small hands you gotta take it all apart to get to anything - that's one thing I love about the XJ, it's all so logical and accessible!

 

judb-

I doubt its the fuel pump because it runs great for the rest of the day once I get it started again. I also can hear the fuel pump 'whirring' like it should when I turn the key to the 'on' position. I drove my Jeep to Macon, GA a few months ago when the problem was happening and it shut down once that morning on the way to work, started back up (after about 5 minutes of cranking) and then I left work early (about 2 hours later) and drove 5 hours to Macon with no problems whatsoever (you would think that if the fuel pump was 'dying' it would have certainly kicked the bucket after hauling *** for 5 hours straight). I spent the weekend there in Macon, drove it around a few times, and it shut down once that whole weekend - including when I made the 5 hour trip back home. After I got back, it started shutting off again soon after. I think you're right about fuel/air delivery because the long trip may have cleaned/flushed out some gunk causing the stalls.

You're wrong about the sensors I think (I hope) because last year I finally took care of all the codes my OBD II was throwing - including the O2 sensor and P0420 catalytic converter codes that were haunting my dreams. I replaced the entire exhaust, happily, put all new sensors in, and my CEL hasn't come on since...even with my current issue.

I'll keep you fellas posted on my progress. I've finally got a chance to do some work this evening.

 

xj maniac-

I'm headed home from work here in a few minutes...before I start ripping apart my Jeep's intake region I am going to check that CPS wire. After I replaced my exhaust last year, including the manifold (header) I remember seeing the bracket for the CPS kinda dangling...maybe its too close. My Jeep is sitting cold right now and I'll check that out first. The only problem I have with your suggestion is that I doubt that after the 'restart' the CPS wire would just magically start working again (especially with a hot manifold) or stop making a difference. Like I posted in the beginning, after cranking the crap out of it and restarting it runs fine the rest of the day, no matter the duration of the trip.

Still, I will give it serious consideration. I'll see if I can find my voltmeter and test the wires.

 

Ha. The Potato Walker...

I guess that makes my name "GusBeater"...

 

I know you mentioned your fuel filter - I was having rough idle and difficult starts on my 96 so as part of trying to fix that I changed it (even though I still had decent fuel pressure at the rail) and noticed a much smoother idle. I'm pretty sure those in-line-can-filters can be partially clogged and restrict flow without a complete blockage. Maybe there is some gunk in yours that settles when the jeep is off, then gets pushed against the screen when the pump primes? I agree that's probably not the main problem you're facing currently, but one thing I've learned the hard way is that one problem is often compounded and made worse by other minor issues! If you haven't changed it in a while, I'd say give that a try too, since it only takes a few minutes and costs less that ten bucks.

I was amazed at how much heavier the old filter was compared to a clean, new one even though it wasn't totally blocked! Plus it'll take strain off the pump and make it last longer. Changing one of those is no fun - that fuel tank lock ring can be a real SOB!

 

When my pump went out (both times) it ran fine while normal driving, but when doing stop & go driving (I deliver mail) it would sputter out at mailboxes & start right back up again like there was no problem. When it finally just died, it was still whirring at "key on" right up to the point that it didn't make a sound.

If you exhaust every avenue you can think of, you may want to just replace the entire fuel pump assembly with a Bosch set up. It could be the regulator going bad & that can cause the pump to malfunction. All that sputtering out every morning can damage your pump. If your pump finally just dies, it may likely not be the pump. It could just have suffered from the main problem.

Again, just something to keep in mind if all else fails.

My best advice is to pay close attention to every little detail at the point the problem occurs & look for patterns.

 

Well fellas, I had a chance to do some work on it last night and I got nowhere except for ruling out a few things.

I didn't do a pressure test on the fuel rail, but I did check to see that I was getting pressure. With the key off, I pushed in that little plunger needle at the test port and a little squirt came out. I assume that meant it was pressurized until I relieved it by pressing that needle. So then I had someone sit in the driver's seat and turn on the fuel pump while I held that needle in and WOOSH I got a high pressure dousing of fuel. So I figure the fuel pump and filter are safe from replacement...for now. But I did not get a pressure reading with a guage so I still plan on doing that. I replaced the ignition coil because that was on my list anyway, then I checked the points in the distributor (which is new-ish) and they had a little corrosion on them, even though the metal was still shiny from being replaced recently. So I cleaned the points and tried to start it up and still nothing.

By the way, the last time I started it up and it died I didn't bother to crank it over til it started again. Now it wont start at all.

I took off the intake hose and looked down into the throttle body. I observed minimal 'gunking' and lots of moisture from fuel. I covered the intake with a plastic plate to "fully" choke it and still no start.

My multimeter was so messed up from being old and crappy that I threw it away rather than testing the CPS with it. Also, there are no markings on the plug for A B and C, so I'm not going to be able to test for conductivity until I get a new multimeter and a diagram of the plug with labels.

I will keep the fuel pump replacement in the back of my mind for now, but I guess my next approach will be to test that CPS.

This sucks hahaha

 

My money is on your CPS. The behavior you've described is indicative. Good that you're going through the process but I'll wager a new CPS will resolve your issue. OEM or NAPA, by the way, avoid Duralast and O'Reilly's if possible.

 

i've got a similar question hopefully you guys can help me out... my 91 xj doesnt start at all right now-been that way since november.... havent had a chance to do much on it. first started when i got to work one day, it died as i was backing up to park. started up just fine so i didnt think much of it but when i left it was running really rough like it was misfiring. checked and replaced the plugs and dist cap-they were pretty bad but then it wouldnt start at all... and thats where its been since.
i have spark, fuel and a new starter. the guys at a local 4x4 repair shop suggested the cps but before digging into it i wanted to ask on here-get some more opinions...

thanks