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Unread 07-08-2013, 07:14 AM   #1
esu
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Opinions on stalling issue

hey Guys, Wanted your thoughts on this stalling issue I have. Ive read some posts and some point to the PCM? My issue seems slightly different and I was thinking a fuel issue at first. Anyway, its a 95 ZJ lmtd 4.0 with 150k miles. The motor is an older renix according to what I could figure out. My son has been using it a little and and started complaining about the jeep stalling and sputtering. Since I am the eternal skeptic and it hadnt happened to me I didnt believe it. I only have the jeep a few months and have slowly been working out the kinks.
This holiday weekend I took it upstate NY on a 2 hour trip. The jeep runs really nice on the hiway. ANyway after an hour and a half at a steady 65 mph a/c on we ran into a traffic accident that shut the hiway down completely. We were idling for about 15 minutes when the jeep just stalled. Several attempts to re-start were negative. It would crank but not fire. Since we were at a dead stop there was nothing to do but wait anyway. After about another 15 minutes they troopers reopened the hiway, the jeep started right up and we started to roll. We only got about 200 yds when a garbage truck that was a few hundred yards in front of us started to burn. Since all the firemen and cops were right there they shut the hiway again. After a few minutes of being stopped the jeep began to sputter. I could keep it alive by playing with the gas but eventually I let it stall completely figuring we were going to be there for a while anyway.
15 minutes later, hiway reopened, jeep started but ran lousy, sputtering etc for about 2 miles till it smoothed out. I left the a/c off this time. It then ran great till the end of my trip.
On the return trip home again it ran great, 65 all the way, cruise on, a/c on and no problems till I stopped for gas a few miles before my house. I left it idling and when I left the gas station it started to sputter again. Sputtered for about 2 miles again till it smoothed out.
At no time did the temp guage spike and it basically stayed in the same area, the hashmark to the left of the 210 mark. In looking at the fuel line it seems they probably could have run it in a better place instead of where it is. I was going to try and redirect it a little or maybe insulate it somehow or am I barking up the wrong tree and should be looking at the PCM? Sorry for the longwinded post but wanted to cover all the details. Thx Cory

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Unread 07-08-2013, 07:38 AM   #2
dellis
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Yes, it could be the PCM. It could also be several other things. I refer you to ZeeJay1997's list of a bunch of stuff that could cause stalling problems.

But, if you want a summary of diagnostics:

(1) Is it only happening around idle? Best I can tell, this is the situation you are describing. If so, then a dirty throttle body and IAC would be the first things that you would suspect. See #10 on ZeeJay's list.
(2) Does it stall when jiggling or moving the connectors to the PCM? Then you have the classic solder problem that ZeeJay notes in the thread linked above (#1).
(3) Can you put a fuel pressure gauge on the rail and measure the pressure at idle and while reving the engine? If it changes significantly during reving - say, dropping from 48 to 30 - then you likely have a fuel problem (pump, erratically blocked filter, etc). A really nice diagnostic is to get a fuel pressure gauge with a longer line, and route it out of your engine compartment to your windshield (hold it down with your windshield wiper), and then watch your fuel pressure as you drive around. Fuel issues are #6 on ZeeJay's list.
(4) When it stalls and won't start, can you be prepared to get out, lift the hood, and check the spark to see if it is a spark issue (maybe carry around an in-line spark tester so that you can see it from the passenger compartment as you crank)? That helps us to understand whether or not the stall is a spark problem or not.
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Unread 07-08-2013, 08:29 AM   #3
esu
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Seems to only happen when idling for an excessive period, then it starts to sputter and eventually stall. If doing short stop and go trips its generally fine. Every time after it happens if you let it sit for a while and "cool" off it starts fine.
It will occasionally sputter like its trying to start when you crank it making me thing more fuel than spark?
And I did change the fuel filter on the frame when I bought the jeep.
I will try playing with the connectors on the PCm and see if it stalls.
I can keep it running although its very rough if I play with the gas pedal.
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Unread 07-08-2013, 08:41 AM   #4
Kingr98
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I had similar symptoms on my son's Dodge Dakota. When it stalled it would have to sit for three to five minutes before it would start again. If I tried to crank it, it would sometimes almot start. Sometimes when it did start, it would run rough for a few minutes before it got going. It would run all day on the interstate.

It turned out to be a cracked ignition coil. I tried several things before I discovered it, but a new coil turned out to be the fix.
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Unread 07-08-2013, 10:22 AM   #5
dellis
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Quote:
Originally Posted by esu View Post
Seems to only happen when idling for an excessive period, then it starts to sputter and eventually stall. If doing short stop and go trips its generally fine. Every time after it happens if you let it sit for a while and "cool" off it starts fine.
It will occasionally sputter like its trying to start when you crank it making me thing more fuel than spark?
And I did change the fuel filter on the frame when I bought the jeep.
I will try playing with the connectors on the PCm and see if it stalls.
I can keep it running although its very rough if I play with the gas pedal.
If it is only happening at idle, then I think your problem is going to be something like a dirty or malfunctioning IAC, dirty throttle body, or vacuum leak.
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Unread 07-08-2013, 11:44 AM   #6
esu
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Quote:
Originally Posted by dellis View Post
If it is only happening at idle, then I think your problem is going to be something like a dirty or malfunctioning IAC, dirty throttle body, or vacuum leak.
I'l take a look at the throttle body, IAC etc. Any thoughts on why its intermittent? Its only done this 3 or 4 times in hundreds of starts and stops.
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Unread 07-08-2013, 11:49 AM   #7
esu
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Quote:
Originally Posted by Kingr98 View Post
I had similar symptoms on my son's Dodge Dakota. When it stalled it would have to sit for three to five minutes before it would start again. If I tried to crank it, it would sometimes almot start. Sometimes when it did start, it would run rough for a few minutes before it got going. It would run all day on the interstate.

It turned out to be a cracked ignition coil. I tried several things before I discovered it, but a new coil turned out to be the fix.
How did you determine it was the coil? Or did you just start swapping things out?
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Unread 07-08-2013, 12:34 PM   #8
Oldfrog
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The first thing you DONT want to do is start swapping out components. That practice gets very expensive. ( dont ask how we know !).

As already stated, methodically go down Zeejay's list and pay particular attention to the throttle body/IAC and the grounding points/ battery cables. A bad battery can do it, a bad alternator can do it, as can a bad ground ( fender well, oil dipstick area, below coil too).

Since it seems to be limited to stalling while at idle or low speeds, dellis has you on the right track with the IAC area. But that could change overnight. It might start bucking at highway speeds at some point.

Dont skip over things on the list and dont just look at the grounding connections, thinking they are clean and tight. Remove the negative battery cable....then start removing and cleaning the 3 grounding points.

I would only add this:

Open the distributor cap, spray electrical contact cleaner in the top of it and wipe it out. Then remove the plate below it, ( cam pickup sensor), spray the sensor area and wipe it, then spray and wipe down the rotating metal plate below the cam sensor plate. Make sure your coil wire, as it leaves the top of the distr. cap doesnt cross any plug wires.

We've all had to deal with issue at least once....and it comes back in a different area from time to time. Jeeps hate dirty power connections, they hate bad batteries, but they love mud !
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 07-08-2013, 02:31 PM   #9
esu
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"Since it seems to be limited to stalling while at idle or low speeds, dellis has you on the right track with the IAC area. But that could change overnight. It might start bucking at highway speeds at some point."
It does buck at hiway speeds for a few minutes till it smooths out. Thats why i was leaning towards something, I dont know what, getting hot or overheating and causing the issue. As soon as you get moving and air starts flowing into the eng compartment it runs better, at least that was my feeling. kinda like "vapor lock" on some 60s cars.
I have changed out the plugs a few weeks ago and planned to do the cap and wires next. Maybe this weekend for those. I will take a look at everything else mentioned so far and see where that leads me.
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Unread 07-08-2013, 02:52 PM   #10
dellis
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Quote:
Originally Posted by esu View Post
I'l take a look at the throttle body, IAC etc. Any thoughts on why its intermittent?
An IAC is like a piston that moves in and out. If dirty, then the dirt can clog up the smooth in-out operation - binding it up.

It is also an electrical component (a solenoid). In my experience working on old pinball machines (which use a billion solenoids to push that metal ball around), a weak solenoid struggles to activate - it looks like a 4-year old trying to push a bowling ball down the alley. It can still do it, but it can sometimes be really slow or work erratically depending on its mood.
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Unread 07-08-2013, 02:59 PM   #11
Kingr98
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I got lucky with my ignition coil. I certainly am too cheap to just start changing things out...

I was going through the same checks for my truck as Zeejay has on his list without any improvement yet. One night I was driving in a heavy rain and my truck started studdering worse, then it stalled. The next day i used a hose in my engine compartment to splash water on different components to see what had an effect. At the time, I was not considering the ignition coil until I accidentaly splashed water on it and the truck died instantly. I removed the coil and you could see that the terminal was bent and there was a crack acros the bottom of the terminal. I replaced it thinking that I was solving a problem with driving in the rain. It turns out that it also fixed all of my stalling problems.

I think that with it being cracked, it was building up extra heat or something and had to cool down before it would operate correctly. I am not a mechanic, so that is just a SWAG.
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Unread 07-08-2013, 10:16 PM   #12
Oldfrog
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Yup that's a known problem area....and one we tend to overlook sometimes.
Mine failed to start today for the first time in 1000 miles. Rained yesterday too....but I never drove it. Wiggled the PCM connectors ( again) and it started right up, but I had been noticing that every once in a while it would stumble as soon as I started it lately. I would just turn the key off and hit it again and it started right up. Not today....so I have a new project on my agenda this week: Track that issue down like a bloodhound and kill it. My guess is that it's time to clean the throttle body again.
__________________
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 07-17-2013, 07:40 AM   #13
esu
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Ok, just a quick update. Its definitely not the coil, swapped it out with an extra my buddy had. Yesterday I got stuck with it driving around town. Soon as the temp guage started flirting with straight up it began to sputter eventually stalling. Sit for 10 mins and it starts up. Got it home and started with some carb/throttle body cleaner to clean things up. Let it run with the hood up for 20 mins and it was fine. Soon as I closed the hood and the temp started rising it started to sputter. Should mention I played with the ECM/PCM connectors and it made no difference in how it ran. Im thinking about flushing the radiator, re-filling with fresh coolant and also putting in a new thermostat, for all I know there isnt even a thermostat in there. If this keeps it cooler it might just help and is not terribly expensive to do and was on my list anyway. I realize this may just be a bandaid for an underlying problem but right now I need to get this thing running semi-reliably. Also going to check and clean the grounds this weekend.
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Unread 07-17-2013, 08:49 AM   #14
dellis
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Hmmm. Is the problem still only at idle, or is it now migrated to a temperature problem? If still only an idle problem, did you clean the throttle body and the IAC?

If however, you are now able to see a pattern where temperature is causing the stalling and the Jeep will not start, then I would first see if it is due to an electrical component ... hopefully not something like a head gasket problem.

If I am to assume it is an electrical problem, you will need to do some testing to determine which one is causing the problem. The next time you have stalled and the Jeep will not start:

(1) Test for 12V at your fuel injectors as you are cranking your engine.
(2) If 12V is present, check to see if you have spark at your plugs while cranking your engine.

If you do not have 12V at your fuel injectors:
  • Switch your ASD relay with another good relay (horn, A/C) and test again.
  • Unplug the connector to your crankshaft position sensor (CKPS), turn the key "on", and see if you have 8V (pretty sure it is 8V on a '95, but it may be 5V) on one of the wires going to your CKPS. If you DO, then you will need to do further testing on your CKPS. If you DO NOT, then additional testing will need to be done on your PCM, connectors and wiring harness.

If you do have 12V at your fuel injectors, but you do not have spark:
  • Coil would be the first thing to check ... but, you say that you've already tried this.
  • PCM would be the only other electrical thing that I can think of that would cause this failure.

If you do have 12V at your fuel injectors, and you do have spark:
  • The IAC is still suspect. Clean and or replace.
  • Switch your fuel pump relay with another good relay (horn, A/C) and try again.
  • Outside of that, I think you are looking at a fuel or mechanical issue.
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Unread 07-17-2013, 09:49 AM   #15
Kingr98
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How high is your temperature going? On my 98, straight up on the temperature gauge is about 210 degrees and mine runs there all day long.

What I am saying is, if your temperature is around 210 degrees, it doesn't seem like radiator flush/thermostat would fix your problem. Although I am sure it is a good maintenance procedure to routinely flush your radiator, I would expect your temp to still run around 210 degrees.
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