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Unread 10-10-2013, 12:54 PM   #1
Blown5pnt4
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1997 ZJ 
 
Join Date: Oct 2006
Location: Huntington, NY
Posts: 94
help me fix this thing

My 97 4.0 zj has an intermittent stall thats driving me crazy. So far I've done the following

New cap
New rotor
New plugs
New msd coil
New air filter
New sensor in the distributor
Top end clean service from local shop
New battery

After all this it seemed to run amazing for a few days and now it's back to crap. I noticed the negative battery terminal looked a little mangled when swapping the battery so I'm thinking of changing that but not sure if it'll help. How many engine grounds are there ? where are they so I can try cleaning them ? Fairly confident its not the pcm as it was replaced 2years ago with a quality one as was the cps. I just want to stop wasting money on it. Lmk any suggestions. Thanks.

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Unread 10-10-2013, 01:35 PM   #2
jm8881
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1996 ZJ 
 
Join Date: Oct 2005
Location: , California
Posts: 454
Always start with this:

12-things-you-can-do-when-your-zj-stalls

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Unread 10-10-2013, 09:51 PM   #3
CDRFunkmeyer
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1994 ZJ 
 
Join Date: Jan 2009
Location: Bellflower California
Posts: 80
No codes? yes I'd say the mangled negative battery cable could matter. The wiring harness should have it's own bolt in the bottom of the engine. Follow the harness back from the battery.
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1994 Grand Cherokee Limited 4x4, 5.2L magnum,
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Unread 10-10-2013, 10:14 PM   #4
Blown5pnt4
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1997 ZJ 
 
Join Date: Oct 2006
Location: Huntington, NY
Posts: 94
Quote:
Originally Posted by CDRFunkmeyer View Post
No codes? yes I'd say the mangled negative battery cable could matter. The wiring harness should have it's own bolt in the bottom of the engine. Follow the harness back from the battery.
The cables look good it was the terminal that was mangled looking. I put in new ones tonight as well as jiggled the pcm connections and swapped the fuel ppump relay. Seems good now but its done that before....
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Unread 10-11-2013, 10:46 AM   #5
Donnyd21
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1998 ZJ 
 
Join Date: Sep 2012
Location: Moore, Oklahoma
Posts: 165
Ecu
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Unread 10-12-2013, 07:00 PM   #6
ZeeJay1997
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1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
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anytime a PCM behaves for a few days after a battery disconnect, then starts crapping out, it is highly suspect.

when does the stall occur? at idle, cruise, accel? what happens to the gauges? lights? if the cruise is on, does it turn off when the the stall occurs?

are any codes stored?
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Unread 10-12-2013, 07:10 PM   #7
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,247
Quote:
Originally Posted by ZeeJay1997 View Post
anytime a PCM behaves for a few days after a battery disconnect, then starts crapping out, it is highly suspect.
This ^

The making and breaking of the battery power can't be good for the PCM....and I 've always suspected that it's ONE of the causes of PCM failure. It it makes you feel any better, I'm on my 5th PCM and so far, so good....
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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 10-13-2013, 10:16 PM   #8
Blown5pnt4
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1997 ZJ 
 
Join Date: Oct 2006
Location: Huntington, NY
Posts: 94
Quote:
Originally Posted by Oldfrog View Post
This ^

The making and breaking of the battery power can't be good for the PCM....and I 've always suspected that it's ONE of the causes of PCM failure. It it makes you feel any better, I'm on my 5th PCM and so far, so good....
Ugh I don't know if I have it in me to go thru 5 pcms lol.

Quote:
Originally Posted by ZeeJay1997 View Post
anytime a PCM behaves for a few days after a battery disconnect, then starts crapping out, it is highly suspect.

when does the stall occur? at idle, cruise, accel? what happens to the gauges? lights? if the cruise is on, does it turn off when the the stall occurs?

are any codes stored?
The stall generally happens after its been sitting for an extended amount of time. Like over night before work the next day. I can hit the remote start to warm it up for a few and it always starts right away. It normally then runs for around a minute then stalls itself. After a second for the remote start to reprime itself it starts and stays running till I get in it. Most of the time that's pretty much the end of it. But sometimes when Im driving to work, when Im approaching a red light on the brakes, it'll just die as if all power to everything was cut. Also sometimes When I get on it, like merging onto the highway or a busy road it'll stumble or die and very very rarely backfire. I don't know what else to replace.....Even though it was replaced I think a year or so ago Im starting to think it is the ecu again, but if I start it, and jiggle on the wires at the pcm it doesn't do anything. Doesn't force the stumble or make it run any smoother. Doesn't leave any check codes. Where is the best place to buy a PCM from ?
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Unread 10-13-2013, 11:27 PM   #9
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,247
I assume you've gone through Zeejay's list of 12 things to check?
( especially cleaning the throttle body and IAC )

Could still be the PCM, but disconnect the upper 02 sensor connector and see if anything changes. ( besides throwing a code for the sensor).

I am also assuming you have repaired the battery cables and cleaned and tightened all grounding points? ( battery, fender well, below the oil dipstick and below the coil)

Also check the crank sensor using this method:
https://www.youtube.com/watch?v=yp_kK6U8a64

As for where to get a PCM, you can PM Kolak here on the forum, or get an A1 Cardone brand from Oreilly's, etc. They run about $289 or so....give or take $50. But DO NOT buy one from either of those outfits in Florida !
__________________
Cajun Recipes and Fishing tips

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 10-14-2013, 01:09 AM   #10
ZJfamilyfun
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1998 ZJ 
 
Join Date: Mar 2013
Location: Alpena, Michigan
Posts: 161
Quote:
Originally Posted by Blown5pnt4 View Post



The stall generally happens after its been sitting for an extended amount of time. Like over night before work the next day. I can hit the remote start to warm it up for a few and it always starts right away. It normally then runs for around a minute then stalls itself. After a second for the remote start to reprime itself it starts and stays running till I get in it. Most of the time that's pretty much the end of it. But sometimes when Im driving to work, when Im approaching a red light on the brakes, it'll just die as if all power to everything was cut. Also sometimes When I get on it, like merging onto the highway or a busy road it'll stumble or die and very very rarely backfire. I don't know what else to replace.....Even though it was replaced I think a year or so ago Im starting to think it is the ecu again, but if I start it, and jiggle on the wires at the pcm it doesn't do anything. Doesn't force the stumble or make it run any smoother. Doesn't leave any check codes. Where is the best place to buy a PCM from ?
Just a shot in the dark..........but have you thought to diag the remote start system???? Who installed it? A shop? You and a buddy? Are all the connections good?? Just a thought being its tied into the starting/ignition system.
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Unread 10-14-2013, 07:54 AM   #11
newfieZJ
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1995 ZJ 
 
Join Date: May 2008
Location: , Alberta
Posts: 6,523
Quote:
Originally Posted by Oldfrog View Post
Could still be the PCM, but disconnect the upper 02 sensor connector and see if anything changes. ( besides throwing a code for the sensor).
O2 sensors can do some weird things . Most times , the issue develops during the warm up cycle where the PCM controls most everything on settings vs using the sensors . Case in hand , the 02 . One case I saw the jeep would go into convulsions for about 30-45 secs , run perfect before and after . Just one example . No CEL .

I'd have to try this before buying anything . A wanky 02 could be the issue . Should run fine with it disconnected , PCM will compensate .
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Unread 10-14-2013, 01:12 PM   #12
chalkboard
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1997 ZJ 
 
Join Date: May 2013
Location: SoCal, CA
Posts: 72
Clean/Lube PCM connections

I too faced the stalling issue with my '97 4.0. For me, cleaning the pcm connections, both sides with deoxit, and then applying pin-head amounts of dialectic grease to the female side connectors resolved my issues. I didn't just smear the grease on the female side. I made sure it made it into each independent female lead. The connector face remained free of grease.

OldFrog and ZeeJay know much more than I do about this issue, but that is what worked for me. I actually traced my problem to the number 7 pin.

Good luck!
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Unread 10-14-2013, 07:21 PM   #13
ZeeJay1997
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1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,905
Quote:
Originally Posted by ZJfamilyfun View Post
Just a shot in the dark..........but have you thought to diag the remote start system???? Who installed it? A shop? You and a buddy? Are all the connections good?? Just a thought being its tied into the starting/ignition system.
This crossed my mind also. When it's time to fish or cut bait, it would behoove you to disconnect the system and see if it's the problem. Any type of add on electronics on these things makes me nervous.
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Unread 10-16-2013, 12:45 AM   #14
kachink
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1998 ZJ 
 
Join Date: Sep 2010
Location: Lake Forest, CA
Posts: 523
Your post above says it stalls when idling after a remote start and when braking. When I had a random stalling problem I finally noticed that it was only stalling when I didn't have my foot on the gas. I removed the throttle body and thoroughly cleaned it, including the IAC and the pocket under the IAC. It didn't stall again for a couple of years.
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