ZJ 96 4.0 stalling and acceleration cutting out. - JeepForum.com
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Unread 01-29-2014, 11:03 AM   #1
Ambidextrosity
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1996 ZJ 
 
Join Date: Jan 2014
Location: Caldwell, ID
Posts: 8
ZJ 96 4.0 stalling and acceleration cutting out.

Hello, another "my jeep stalls on me?!?!" Post for all you ppl. So I'll start by saying if you only drove this occasionally on short trips you wouldn't know it had any problems(isn't that always the case :P) Anyway lately, usually after the jeeps been driven quite a bit that day, it will stall while idling or lose power( gas pedal becomes unresponsive, doesn't respond to pumping) while cruising at various speeds. It doesn't always dies after it stops accelerating, today was the first time it stalled after power loss actually, but when it does die it shakes and sounds pretty clunky? The CEL has only come on once when it stalled that I can remember. It's been having some issues since about late august and here's what has been done and what I've done since it first has had issues.
-Ignition coil (when prob first began it gave three codes this was one so I changed the coil)
-Catalytic converter ( 2nd of the first initial codes that were read, replaced by a repair shop, second time since owning the car that the cat has been changed, first time only 6 before that, thank god for warranties.)
-Crankshaft position sensor, it's only a couple months old and the one that was bad was put in less than a year ago.
- Cleaned IAC and housing <2weeks ago ( idle seems smoother now but it still will randomly stall at idle.
-Battery only a couple months old
-Water pump/thermostat(I'm sure these are totally unrelated but it's worth mentioning as I would like to be as specific as possible.

So what I'm thinking the problem could be: A. throttle position sensor, due to the loss of power but not total shut off while driving, car shifts erratically or lags during acceleration sometimes so that's my guess. B. MAP sensor, this was the third code the that was read initially but that code hasn't been present since the ignition coil/ cat fixes. I don't know why it's still a suspect but I don't wanna rule anything out completely.

I have other guesses and hunches, but to avoid making my first thread any more long winded I'll stop there for now and let some people hit me with some questions/ suggestions first to get this thang rolling... I did just say thang **shaking head**

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Unread 01-29-2014, 01:13 PM   #2
ZeeJay1997
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my reply for all "my jeep stalls on me?!?!" posts. See link below.
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Unread 01-29-2014, 02:24 PM   #3
Oldfrog
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1997 ZJ 
 
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Welcome to JF. Go through Zeejay's list, as he mentioned.
It almost sounds as if it's heat related. If that's the case, unplug the upstream o2 sensor and drive it a little. (It will throw a code). If needed, replace only with an NTK ( or NGK) o2 sensor. They dont like Bosch sensors.
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Unread 02-11-2014, 09:20 AM   #4
Ambidextrosity
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1996 ZJ 
 
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Location: Caldwell, ID
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Hey so I've been trying to go through and check some of those "dirty dozen" suspects, but my rides been acting up a differently so I thought I'd update my issues. The CEL is on now, giving an ignition/primary coil code and the cat code (p0420). Again the ignition coil was changed and the cat converter is newer as well. I'm gonna try the o2 unplug for a day or two to see if that helps. Lately though it usually will die at an idle, or start to stutter and shake coming to a stop, or it will lose power while accelerating and if I just let it coast and pump on the gas a bit eventually it will catch, not sure if it's the pumping or just the timing that kicks it back up. Also it seems like when I'm idling it won't die, or hasn't died yet, if I throw it in park or neutral??? Anyway just thought I'd post some updates for a more ideas.
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Unread 02-11-2014, 09:34 AM   #5
ZeeJay1997
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the low idle at a stop can be several things, you need to be sure the transmission fluid is at the correct level before you chase electrical gremlins.

the cat code can be caused by the cat or the 02 sensors. disconnecting then is a good approach to see if the driveabiltiy improves.

check tranny, disco o2, and finish the dirty dozen. read #8 carefully and check the coil connector. this may be the source of the coil code
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Unread 02-12-2014, 12:08 AM   #6
Ambidextrosity
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OK thanks for the advice, I did unplug the upstream 02 sensor and tried to drive it home tonight but it hardly made away from my buddies house where I disconnected it, so I pulled over and plugged it back in and I had only one small hiccup(but no stall) the rest of the way home 15+ Miles

Last edited by Ambidextrosity; 04-09-2014 at 09:21 PM..
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Unread 04-09-2014, 11:29 PM   #7
Ambidextrosity
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Hey its been a while since Ive given any status uPdates on my ride. So as of recently after taking it to a local mechanic who told me that all signs Pointed to the PCM as the culPrit to the issues its been having with the catalyst code and ignition coil code, as well as the intermittent stalling issues. When I went to Pick up my car from the guy which had been sitting there for a couple days the battery was dead. The battery wasnt that old (<6months) and seemed fine before hand so I thought it was kinda strange. I gave her a jump though and drove it home, it cut out once and about 35mph but didnt die, it kickd right back up and got me home.

So at home I start the jeep and begin messing with all parts of the wiring harness trying to get it to do something but it doesnt, what it does do is where it starts getting interesting. It begins slooooowly winding down like its running only off of the juice in the battery. eventually it dies. I jump it again, it starts, take off the jumper cables and it begins winding down. Immediately I think, Alternator! So I take the alternator out and take it to autozone. They throw it on the testing machine and run it a few times but it passes everytime... Alright, so I bring my battery in to give it a full charge and they throw it on the charger and I put the battery/alternator back in and it stays running.

But after starting the car the voltage meter on the dash sits about halfway between 9v and 14v for about a minute and then either drops down to 9V throwing the CHECK GAUGES light on, or it will jump back up to just under 14v where it usually sat. Car will continue to run fine despite what the meter reads. Within a week of charging the battery and testing the alternator it slowly dies after I start it and drive it a few hundred feet. I think, ok the battery might not be holding a charge, so I get a brand new battery. problem persists despite the new battery. I take it to ORiellys and they do a starting system test on the battery/alternator/ etc. while the components are in the vehicle. What their testing tool showed is that the voltage regulator is failing, it passed once but failed all other tests. The voltage regulator in my Jeep is built into the pcm, and I had a replacement sent to me earlier that week.

So i threw the new pcm in and the problem is still occuring. The manual method of extracing DTCs show a #47 which is described as: Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit. Im pretty lost at this point, Im hoping there are some wires I can test with the multimeter I just got that are directly involved with this part of the engine system but I dont really know how to find it them and honestly Im not fully confident how to use a multimeter *sighs*. Does anyone have any insight as to what I need to do next besides light the f-ing thing on fire.

Last edited by Ambidextrosity; 04-10-2014 at 08:45 AM..
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Unread 04-10-2014, 04:33 AM   #8
ZeeJay1997
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hit the enter key every now and then.
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Unread 04-10-2014, 08:38 AM   #9
Ambidextrosity
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Man I honestly, I get going writing these things and don't even realize how long and continuous they run, my bad. ^is that any better.
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Unread 04-10-2014, 12:09 PM   #10
sebian
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There is a wire that runs from PCM to alternator, which triggers the alternator to charge the battery. It is one of the two smaller wires that go into a black block on the alternator. Check the connection there, and trace the wire as best you can to make sure there are no nicks in the shielding. Also, double check all of your engine grounds. Disconnect them, clean them and reattach them. Check your battery cables. I bought my ZJ when I lived in MN, and the battery wires had a ton of corrosion on them where the leads connected to the battery. I had to trim them back a bit, but eventually replaced that whole harness. I would also recommend checking the battery voltage while it is running to see if the alternator is supplying any charge to it. You should be getting a voltage reading ~ 13.5 - 14.5 volts.
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Unread 04-10-2014, 05:14 PM   #11
ZeeJay1997
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thanks. much easier for my old eyes to read, i was on a half cup of coffee this AM when i first read your post.

sebian is spot on with the generator field driver signal (green wire)from the PCM and grounds on the block. also in the equation is generator field source from the PCM (green and violet).

since you are fairly certain the battery, alternator, and pcm are good, there are only a couple of things it can be. whatever it is has to affecting the circuitry inside the pcm because it produces the battery gauge reading across the CCD bus to the IP, and it is not right (still?).

so i would disconnect the battery, alternator field, and pcm, then check the two wires that were connected to field terminal to the disconnected negative battery cable for a short to ground. there should be no continuity on any range. then check each wire individually from point to point for zero ohms between terminations.

there are plenty of youtubes about how to use multimeters. they aren't that complicated. i also posted a link in the dirty dozen to the fluke website. dig around there
charging.jpg

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Unread 04-12-2014, 05:23 PM   #12
Ambidextrosity
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So Zeejay, on the two top field terminal connectors I'm not supposed to have any continuity between them and the negative battery cable? I wasn't sure what you meant by there shouldn't be continuity on any range?
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Unread 04-12-2014, 07:48 PM   #13
Ambidextrosity
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So my update for today:

Took a voltage reading on my battery before I went to work( on the jeep that is). It read about 13.45-13.49.

Disconnected all the grounds and REALLY cleaned them, I took my time and was very thorough.

Took a voltage reading after it was all said and done, read 13.5-13.53. I guess it helped but if the voltage varies between 13.5-14.5 is being on the lowend pretty normal? Also I took the reading while the car was idling and without using any accessories, I didn't have an extra hand to help but if someone gave it gas while I was running the test would the voltage go up due to the alternator working harder?

Also just thought I'd mention that I have done quite a bit of driving since I changed the PCM and the two initial codes I was having a problem (catalyst system/ignition coil) haven't popped up at all. I know every time you disconnect the battery it drops the codes, but I drove around it for about 2 days on the freeway and off and no CEL. normally with the old PCM the codes would shoot after driving it a couple times after they were cleared, I can't rest too easy yet but I've got some good feelings about the new PCM. Plus the new one looks slick hah, the old one looked a bit decrepit.

Last edited by Ambidextrosity; 04-12-2014 at 08:09 PM..
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Unread 04-12-2014, 08:43 PM   #14
ZeeJay1997
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Quote:
Originally Posted by Ambidextrosity View Post
continuity on any range?
since i dont know if you are using an auto ranging or a manual meter, it's important that you check it on the higher ranges. if you have it on 200 ohms range and there is more resistance in the circuit than 200 ohms, some meters will show an overload on the display. someone unfamiliar with the meter may not recognize this and read it as no continuity. on the other hand, if you have it on a higher scale and a low resistance exists, the display will read several zeros which may lead the inexperienced user to believe there is a dead short (near zero ohms).

bottom line is you have to know how to read the display on the meter.
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Unread 04-12-2014, 11:13 PM   #15
Ambidextrosity
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It's a manual range, I'm using an innova 3320 if that helps. But I did test both the field terminals on the 200 ohm setting, one jumped up to a bunch of higher numbers but dropped to zero almost immediately, the other had no effect, the display read: 1, which is just what's on the display before you perform any test. Does that help give you a better idea? But now that I know what you mean by " on any range il have to go back and retest on the other ranges.

Last edited by Ambidextrosity; 04-13-2014 at 12:45 AM..
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