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Unread 09-12-2012, 11:10 AM   #1
cherub2him
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1996 ZJ 
 
Join Date: Sep 2012
Location: Dacula, Georgia
Posts: 7
ZJ Stalling

Grande Cherokee 4.0 L 6cyl. Mi = 245,061

Been having a lot of problems with stalling only after I replaced my fuel filter 2 months ago. The obvious problem would have been the filter facing the wrong direction, but it's going the right way. The stalling happens in one of two ways: an absolutely silent shutoff (cab still has full electrical power, but engine just loses it) and then a puckering, glub-glub stall.
I thought it was an electrical issue which OBD readings said the ignition coil was bad: replaced that along with the distributor cap and rotor (all were rusted and nasty). My alternator is a little low, but the mechanics said it wasn't in danger of needing replacement, and the battery is brand new. Changed the spark plugs last year with OEMs and just checked them Saturday and they are doing fine.

I have cleaned the throttle body, cleaned the IAC sensor, and checked the fuel pump relay. I haven't had any problems with stalling in over a year and a half until I changed this fuel filter! The PCM was just replaced a while ago, and I even tried to toggle that while idling to see if it would shut off, but it didn't. The fuel pump is working just fine. No leaks in fuel lines either.
On my drive to school, the first 15 mins is highway driving and I have yet to stall there. The second 15 mins is town-area driving with hills and that is where the problems start. My car has now stalled in the exact same place two days in a row with the exact same conditions: on a inclined rode probably about 7-10 degrees above horizontal while sitting at a stop light getting ready to turn. It then continues to stall all the way after that for no reason.

The only thing I can think of is that air is in the fuel line or something like that or maybe the fuel pressure is not where it should be. I was so annoyed this morning that I pulled the fuel pump relay out, kept starting the car like I was changing the filter, and then after the residuel fuel was out of the line, I just kept priming the fuel pump like 6 times to get pressure back into the line. I am so exhausted with trying to figure out what the issue is, please help!????

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Unread 09-12-2012, 12:35 PM   #2
bananaslug
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Location: upland, ca
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It sounds like the problem occurs once its warm. Theres no codes, but perhaps its O2 sensors sending bad info once they get asked. On my 96 its impossible to put the fuel filter on wrong since the inlets and outlets are different sizes. Since youve taken care of the PCM, are you SURE its not the fuel pump? I just replaced mine and when it was dying gave me a coil code once.

For a long shot cheap fix, get some lucas or stp fuel treatment and dump it in and see what happens.
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Unread 09-12-2012, 01:09 PM   #3
tizzly
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1994 ZJ 
 
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Location: schenectady, NY
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I was having a similar problem a week ago, leave work and drive to Wendys and stall out at the window. 3 days in a row.
what i did- i took the o2 sensor out and sprayed the crap out of it with T.B. cleaner. Pulled off the T.B. and made a cork gasket for it, pulled the IAC, cleaned a month ago, it was clean. pulled the TPS looked fine. Pulled the MAP and sprayed T.B. cleaner through the passage. put it all back together and i put a zip tie on the MAP's tiny vacuum line b/c it was loose. Installed a thermostat (180), it didnt have one, and today i cleaned and re-gaped my spark plugs. I also opened up the idle screw on the T.B. a hair.
No telling what fixed the problem but one or all of these things did.
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Unread 09-12-2012, 01:10 PM   #4
tizzly
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1994 ZJ 
 
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I was having a similar problem a week ago, leave work and drive to Wendys and stall out at the window. 3 days in a row.
what i did- i took the o2 sensor out and sprayed the crap out of it with T.B. cleaner. Pulled off the T.B. and made a cork gasket for it, pulled the IAC, cleaned a month ago, it was clean. pulled the TPS looked fine. Pulled the MAP and sprayed T.B. cleaner through the passage. put it all back together and i put a zip tie on the MAP's tiny vacuum line b/c it was loose. Installed a thermostat (180), it didnt have one, and today i cleaned and re-gaped my spark plugs. I also opened up the idle screw on the T.B. a hair.
No telling what fixed the problem but one or all of these things did.
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Unread 09-12-2012, 04:05 PM   #5
cherub2him
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@Banana: I mean everytime I turn the key to the on position I hear the whirrling from the fuel pump. I know though that it is atleast getting power, but I probably shouldn't assume that it also means it is working properly. It would be weird though for it to go bad only shortly after I changed the fuel filter. Could I possibly have a defective filter? I'm definitely going to try the fuel treatment! Thanks man.
@Tizzly: Appreciate it, I'll try checking and cleaning all that and see what happens.
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Unread 09-12-2012, 04:14 PM   #6
tizzly
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I also changed my pump about a year ago b/c the sending unit for the gauge was done, i kept the old one for a back up, after all it still pumps. lol
when you changed the filter the flow in the pump may have increased and it may be clogging the in tank filtration with sediment from the bottom of the tank, not sure if that would be possible.
last thing id check
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Unread 09-13-2012, 06:21 PM   #7
cherub2him
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The clogging idea sounds pretty possible to me (but I'm not a mechanic so I guess not too much credibility there, lol). I'm having a full diagnostic test done on Friday night/Saturday morning and I will let you guys know what the guy finds and if things get fixed.
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Unread 09-18-2012, 08:49 PM   #8
cherub2him
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All right so here is an update after talking to the mechanic: the clogging theory is definitely possible especially if the filter hasn't been changed in a looong time (mine hadn't been changed in 12 years). However, I changed the filter again just for the heck of it, and absolutely no sediment flowed out of the filter--only clean gas. So in this case, that was not the issue. Now here is the big thing: Keep in mind that the guy I went to worked for a Chrysler dealership for 20 years specializing in diagnostics. Currently, he is a one-man-crew, independent shop. He knows his stuff and is one of the most honest mechanics I have ever met (I mean, he spent an hour+ on the phone with me just trying to trouble shoot and telling me his experiences with this type of thing) Unbeknownst to me, my neighbor has recommended that guy to a lot of people.

The problem lies (once again!) in the PCM. I thought that was taken care of since it was replaced not too long ago, but that is not the case. He told me that PCM problem in the 96 ZJ's were about the worse and the 97's only got a little bit better. He still to this day doesn't know the problem nor does Chrysler really know. Whenever they came across this "PCM" problem at the dealership, they put a new one in and sometimes saw within a day, a month, or whatever that same car come back in and the computer code for the "bad PCM" would pop up. (When he ran the scan on my system the PCM code was the one that came up many times).

Here's the crazy part. When they sent these "Bad PCM's" back to be tested for a bad resistor or something wacky in the computer board, almost all of those "Bad PCM's" were sent back to them with a guarantee from the testers that there was nothing wrong with the computer board. No bad resistors, shorts, nothing. His only theory was that the way the pin connectors aligned was a possible issue, but they did everything to make sure those were secure (adding dielectric grease etc). He did say that with some models the entire problem was that water was getting into the pin connections and you could tell because there would be like water stains in the connector area. (I forgot which models he said though.)

Anyways, when he was telling me his theories, that sparked my memory of a website I came across a long time ago when this problem was happening. It's www.dyingjeep.com I have taken a gamble for $20 bucks to see if their proposed fix actually fixes it. I was kinda like, "either $475 for a new PCM, or $20?" Luckily, they accept paypal so, being a security freak like I am, I was comfortable with that. If all else fails, I'm out $20. If it was a scam, paypal would fight it for me. So I installed their mod last night and even added my own mod. I drove the car today fairly hard (sped up then quick slow downs, hardder stops, idling for a long time), and Thank the Lord, not even so much as a sputter. We'll see what happens this next week and if this really is the fix. Even if this mod doesn't fix the problem, these guys seem to be on the right tract entirely to which I will investigate further until I have the absolute answer. The mechanic was very intrigued by their theory and wants me to keep him updated too. If it doesn't work, he and I are going to pull apart that pcm. Since I didn't find the answer myself and dyingJeep.com is charging for it, it would be entirely unfair to reveal their findings on this forum. If it works though, I will with 100% confidence condone dyingjeep.com and let you all know that $20 is entirely worth it.
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Unread 09-18-2012, 09:04 PM   #9
ZeeJay1997
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Hope it works out for ya

Give it a week before you break out the champagne and party hats.
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Unread 09-19-2012, 12:34 AM   #10
bananaslug
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Dont pay 475. Here:

http://www.oreillyauto.com/site/c/de...6&ppt=C0334#at

I need one as well. Fuggin 96s are cursed I guess.
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Unread 09-19-2012, 11:44 AM   #11
JS97ZJ
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After you've wasted your money, do the 12 point check....

http://www.jeepforum.com/forum/f13/1...talls-1407423/

And if that doesn't clear it up, this should do it for you...

http://www.jeepforum.com/forum/f13/9...tures-1303589/
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Unread 09-25-2012, 08:38 PM   #12
cherub2him
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All righty: So it's been a whole week of driving and absolutely no stalls......which I haven't been stall free for a week of driving in I don't know how long. It has had every opportunity to just cut out in the exact same areas it had been stalling everyday, but it's been good. Thank the Lord. @Zeejay97: party hats are out, lol.
Even if this is only a fix that works for a few weeks, stalls once, and then works a few more weeks: I'll take it. Engine idle has been a little strange, but it's leveling out. It's always weird though since the engine starts going rough when I start braking below 25 mph. Feels like a super grab or something from the rear pads......I may need to check those pads.....hmmmmm. Anyways, I think I'm going to change the catalytic converter and muffler out since they are 16 years old and probably causing performance issues. The muffler looks ridiculously dented and possibly pierced. The cat is only welded on the end to the muffler which is welded to the tailpipe......any thoughts about what to do and the best parts to get?
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Unread 09-25-2012, 09:08 PM   #13
bananaslug
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So the "Dying Jeep" fix was what worked? If so, from what I have read, its just a temporary fix. Just out of curiosity, what type of PCM did you replace your old one with last year?
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Unread 09-25-2012, 10:42 PM   #14
Uniblurb
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I also have a 96 4.0 and one thing I haven't seen in this thread is checking to make sure the engine grounds are clean/good. Before I knew better, had the dealer replace my PCM with a reman unit (ACR), and it didn't even last a year. Now you would have thought they would have checked to make sure the PCM ground on one of the coil studs was clean/good but they didn't. This ground is critical since it grounds the PCM and then all the sensors are grounded through the PCM.

Luckily my reman PCM was under warranty and installed another myself. But I cleaned all my corroded/rusted engine grounds 1st. Have a feeling the bad ground on the coil stud caused my OE PCM to fail along with the first reman PCM. 2nd reman unit is holding up good, knock on wood.

BTW, ZeeJay was a great in helping me figure this problem out! You can see #8 "Grounds" in his below thread, which was previously posted, but worth posting again.

http://www.jeepforum.com/forum/f13/1...talls-1407423/

Since your engine is running rough when braking below 25mph you should check for a vacuum leak. Particularly the hose on the far left of the intake going to the brake vacuum booster and the rubber grommet on the booster itself the hose attaches to. I put RTV on the rubber grommet where it goes through the metal on the booster and this solved my leak problem.
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 09-26-2012, 08:02 PM   #15
cherub2him
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@Banana: It's working pretty well so far. I also made a slight mod to it though by adding electrical tape as an insulator to eliminate any electric interactions. I don't know what brand the PCM is, when my dad had the car, he bought it so idk.
@Uniblurb: where is this PCM ground on the coil stud exactly?? Is it behind the PCM? I'll def take a look at that one. I checked the vacuum hose for leaks by just kinda nudging it while the engine idled but nothing happened. I guess that means it's ok I suppose? Something I found very interesting though is that when I accidentally rolled up my windows and just held the switches up, the engine idle really dropped. Released it--went back to normal. I'm thinking an alternator issue? when I had it checked a month ago, the guy said it was low but not in dire need of replacement. And you're right man, Zeejay's 12 points is def good stuff. I've read it before . Until you said that though, it didn't dawn on me that THE Zeejay97 was in this thread!
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