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Unread 06-08-2013, 09:10 AM   #16
chalkboard
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1997 ZJ 
 
Join Date: May 2013
Location: SoCal, CA
Posts: 69
Update

Update: Well, my ZJ has made it through 2 more weeks of mixed daily driving without any stalls. This makes a total of 3 weeks altogether. It really is unbelievable. I will update again in a month, if I remember.

Sorry Frog, I did wash it and am working on other issues, hopefully your ZJ wont hear.

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Unread 06-08-2013, 12:04 PM   #17
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
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Now you've gone and done it !

Update on my stalling: Since I cleaned the crud and oil out of my distributor cap and under the pickup coil plate in the distributor, no stalls for over 250 miles. At the same time, I rearranged my coil wire as it left the distr. cap so that it didnt cross any plug wires along the way to the coil. I also re-cleaned and re-seated one of the PCM connectors at the same time. No telling which of these fixes "cured" the stalling. Maybe all 3.

I was getting the coil code on my code reader after the stalls.
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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, 01:41 PM   #18
chalkboard
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Final Update

Final update: It has now been almost 2 months of trouble free driving since cleaning and lubricating my pcm connections. I really wish I had known about this forum years ago and I would like to thank JF and all those who have taken the time to share their experiences here.

If I had it do over again, I would not take it to any mechanic, as all I got was years of wild goose chases and overpriced estimates and no fix. I had no excuse to take it to them, especially since I'm an experienced wrencher, having blueprinted engines in my youth, I should have just tackled the problem myself. Oh well, lesson learned.

Things I learned: I believe a lot of people replace coils at the first sign of a coil code with no joy. On my '97, the number 7 pin is responsible for generating this code. If you test the wire it will test good. The connection will even pass the wiggle test, however, it can still be failed in its installed state. A bad connection here will toast your PCM. I believe a lot of peeps out there put in PCM after PCM only have this lead (or another) short them again. Oldfrog has info on how to repair these plugs. In my case, I was working with a JY wiring harness installed by a local mechanic before they gave up on it. I carefully cleaned and used dialectic grease on each pin and this gave me my joy.

Note: I had to replace the battery during my repair. The conventional wisdom here on JF suggests a weak battery could cause stalling issues like I had. So for completeness, my battery was five years old and had been starting the jeep up until the day I did the repair. However, when I took it in for testing, it failed the load tests.
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Unread 12-30-2013, 04:04 PM   #19
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Not so Final Update

It's been 8 months since I cleaned the pcm connectors the first time, and unfortunately, the stalling has returned; in addition I tried to do a quick clean a couple of months ago which really didn't make much difference.

So, if you clicked "view unread," I'll try to summarize what's happened in the past, if your reading first time, then skip this paragraph,,,,,,,. Four or five years ago, I took it in to the stealership for the stalling issue. They quoted me over 2000.00 to fix (splice new harness connectors and new pcm.) I then took it to an independent who I let put a new pcm in it; this worked for almost a year and the stalling returned. I took it back under warranty, they put a new engine harness (salvage) and pcm in. It drove fine for a few months, then back to stalling. I then cleaned the connectors myself and got nearly 8 months of trouble free driving bringing me to the here and now.

In the past, I was told by the stealership that the coil and all sensors were good. This was confirmed more recently by the independent. So I must be missing something. I tried to recall when it first started stalling and finally remembered, it started right after the stealership put a new key cylinder in it. I had taken it in because I had slammed it into park fouling my linkage and key cylinder. Is it possible they could have damaged my ignition switch all those years ago? Could a damaged switch even cause the car to stall at any speed? Or is the switch taking out my pcm?

So my real question for the Jeep gurus,,,Is it possible to test and diagnose an ignition switch successfully?

Any thoughts are appreciated!
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Unread 12-31-2013, 08:34 AM   #20
SchizophrenicMC
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Two things. One: Check out ZeeJay's thread on the "Dirty Dozen" things that typically cause the ZJ's stalling issue.

Two: Yes, the ignition switch can cause the car to stall at any speed. If it loses contact briefly, it can potentially cut power to the PCM, and in turn the engine ceases to run. As well, it can short the PCM if certain conditions are met. I suggest keeping that switch in mind for further diagnostics.
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Unread 12-31-2013, 07:53 PM   #21
Oldfrog
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Hello again my friend. Sorry it's acting up.
Here are a few things I have learned about mine, since you first had your issue:

1. Wiggle the wires ( dont be shy about it) on the IAC and TPS connectors with the engine running. If the idle changes....look there.
2. I swapped out my o2 sensors..( ntk, of course) as well as my 5th PCM at the same time. My theory was that the cheap o2 sensor(s)...shorted and fried the previous PCMs.
2500 miles later.....it's fine....except the occasional stutter at startup due to the aftermarket IAC and TPS, which I have bought from the dealer, but not installed yet.
__________________
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 01-01-2014, 02:59 PM   #22
chalkboard
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Quote:
Originally Posted by SchizophrenicMC View Post
Two things. One: Check out ZeeJay's thread on the "Dirty Dozen" things that typically cause the ZJ's stalling issue.

Two: Yes, the ignition switch can cause the car to stall at any speed. If it loses contact briefly, it can potentially cut power to the PCM, and in turn the engine ceases to run. As well, it can short the PCM if certain conditions are met. I suggest keeping that switch in mind for further diagnostics.
Thanks Schizo,,,,,,,,,I have read ZJ's dirty dozen many times. And you can bet I will be diagnosing the ignition switch. I believe I may have a way to do it while driving and maybe I can pinpoint it as the cause, or at least eliminate it. I will post back if the test works.
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Unread 01-01-2014, 03:12 PM   #23
chalkboard
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Quote:
Originally Posted by Oldfrog View Post
Hello again my friend. Sorry it's acting up.
Here are a few things I have learned about mine, since you first had your issue:

1. Wiggle the wires ( dont be shy about it) on the IAC and TPS connectors with the engine running. If the idle changes....look there.
2. I swapped out my o2 sensors..( ntk, of course) as well as my 5th PCM at the same time. My theory was that the cheap o2 sensor(s)...shorted and fried the previous PCMs.
2500 miles later.....it's fine....except the occasional stutter at startup due to the aftermarket IAC and TPS, which I have bought from the dealer, but not installed yet.
Hi Frog,,,Its been awhile. Happy New Years to ya and other forum members!!

I'm glad to hear yours is behaving as it should. I wiggled the wires as you suggested and I got no change in anything, in fact I have wiggled every wire under the hood and have found nothing. I'm sure the O2s are original, but I need to crawl under there and verify it. As you may recall I am on my second wiring harness and it is doing the same thing, so I believe my problem is outside of the harness unless I'm just really unlucky. I am going to go through ZJ's list again, as I never did clean the PDC. I am also going to remove the coil and check for cracks, though it tests good. My stall can be characterized as only occasionally sputtering before dying, more typically, its as if you just turn it off with the key. It happens at any speed, anytime, cold or hot.
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Unread 01-02-2014, 08:23 AM   #24
Oldfrog
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1997 ZJ 
 
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That sounds like a bad PCM, but maybe not.
It could be something simple like a loose connector plug....maybe at the coil, etc. When mine was acting up the last time, I'd leave the key on after the engine died, rush out, pop the hood and check for 5 volts across the TPS connector. It was indeed, still 5 volts. I'd reinstall the connector on the TPS and it would start. Go figure.

Go ahead and order that new upstream o2 sensor ( NTK brand ) from rockauto.com now. It's really cheap and you're going to need it anyway, sooner or later. Who knows? You might get lucky.
__________________
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 09-23-2014, 02:03 PM   #25
chalkboard
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1997 ZJ 
 
Join Date: May 2013
Location: SoCal, CA
Posts: 69
Looking back

After nearly a year of driving since cleaning the PCM connections (again) and purchasing a new battery, I have only experienced an occasional sputter, and only one stall at idle. So technically, I was only able to get it back to 95 percent of normal performance.

If I had it to do over again, I would:

1) just buy a mopar crank sensor upfront, as unless you are the original owner, who knows what's in there. If you don't, you will just wonder if it is the crank sensor, even if it tests good. After all, intermittent means just that. Test drive

2) Next, I would take the truck and have the battery checked at a quality facility. If it is even just slightly out of spec, buy the best battery you can possibly afford, even if the one you have is relatively new. Also make sure the cable to terminal and terminal to battery post are 100 percent free of corrosion. Test drive.

3) Clean the PCM connections using your preferred method. I finished mine off with dialectic grease (it took a couple of goes.) Test drive. If this improves drivability, then consider increasing tension on the pins using the dental pick method (I didn't do this, as the Jeep stopped dying randomly.) Test drive.

4) If you have unlimited amounts of time and are good with a multi-meter, then memorize Zeejay's dirty dozen and dig in (prob should read the dirty dozen first regardless of what you plan to do.) If you do not have the time, or patience, begin looking for another Jeep, and I would suggest not getting a '97 4.0.

5) Purchase different Jeep. I snagged a 2001 WJ Laredo with only 65k and a warranty from the local Jeep dealer. I had to pay top dollar, but the peace of mind was worth it. Sold ZJ to a knowledgeable buyer.

Good luck to all who read this in the future.
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