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Unread 01-16-2008, 12:57 PM   #1
dereckdaniels
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Join Date: Jan 2008
Location: canada
Posts: 4
1990 Jeep YJ Ignition Problems

Hi I have a problem with my 1990 Jeep YJ 4.2 Liter. It will start fine and then keeps shuting down, and then wont start. I replaced the coil, cap and rotor, wires, and plugs. I tested the voltage at the coil power wire and it jumps around from 9 to 7 volts. I am thinking it might be the conector is corroded and not getting a good enough conection. I was getting 13V at the firewall, and from the firewall to the connector was 1.5 ohms resistance in the wire. I am also wondering if its a bad ground. Does anyone know how this coil is grounded, cause if i jumper the neg wire to ground it just shuts off. Plese help.


Last edited by dereckdaniels; 01-16-2008 at 04:24 PM.. Reason: wrong year
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Unread 01-17-2008, 10:51 AM   #2
MRGeep
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2008 JK Wrangler 
 
Join Date: Oct 2007
Location: Winston-Salem, NC
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I was having a very similar problem. My YJ (w/ 4.2L and weber carb) would start up and would run in place for as long as I wanted. Once I put it in gear and put a load on the engine it would stall out and I would have to give it loads of gas to keep it running after I would get it restarted to get it back into the garage after that. I found a short coming from my ignition control module to my coil, but the problem persisted after fixing it. I finally replaced the ICM and now it works with no problem. I would take a good hard look to see if you have any shorts and see if you can get your ICM tested somewhere. It'll be about $60 to replace it if you can't find a place to get it tested anywhere. Worked miracles for me.
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Unread 01-17-2008, 04:51 PM   #3
ctm
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1990 YJ Wrangler 
 
Join Date: May 2007
Location: Boston MA
Posts: 1,429
yup, ignition module. mine tended to overheat and cutout. I bought a new one and I mounted it on the passenger side fender near the horn, it's a cooler spot than under the coolant overflow. no problems since.
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Unread 01-17-2008, 09:42 PM   #4
dereckdaniels
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thank you guys i will try that
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Unread 02-26-2008, 12:41 PM   #5
maximum729
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1990 YJ Wrangler 
 
Join Date: Feb 2008
Location: St. Cloud, Minnesota
Posts: 123
Similar issue

I saw this thread and seen it was the exact problem i was having:

1990 YJ
I-6
4.2L (AMC 258)

Friday I took it out in the fields for a few hours in 4-low literally going 5MPH or less the entire time. Late that evening i was heading up the ditch to head home and It lost all it's power

The jeep would idol GREAT! and if i was in neutral (automatic) it would run fine also even if i reved it up. BUT as soon as i put it in gear and put a load on it (even in 4-low) it would run up to about 1500RPM then start sputtering backfiring. I though it may have been due to the extreme temp changes here in Minnesota so i put a bottle of seafoam in the tank and let it idol. The next morning i started it up and drove the 4 miles into town and it worked great again. As soon as i was coming home it started acting up by backfiring and poping just as it did the night before.

when i got home i let it idol while i was searching around under the hood for maybe some loose vacuum lines. and all of a sudden it just shut off as if i turned the key off... now I've got no spark.

I've replaced the
-pick up coil
-distributor cap
-had the ignition coil tested

Now i tore out the ICM. there is only one place in the area that can test it. they want $10 bucks just to test it... and everywhere in town that i can order it from wants $105-124 for it... If it's bad is there a good place to buy one online? Also, how is the best way about testing to make sure there isn't a short in the wiring?
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Unread 02-26-2008, 04:59 PM   #6
pat8942
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1992 YJ Wrangler 
 
Join Date: Dec 2007
Location: Deming,New Mexico, New Mexico
Posts: 2,178
Back in the stoneage when I worked at the Ford dealer we used to pour cold water on the hot Duraspark (Same thing in older Jeeps) module and if it started it was the module other times you could tap it with a hammer and the car would quit.
These are some primitive test methods but they worked.
Quote:
Originally Posted by ctm View Post
yup, ignition module. mine tended to overheat and cutout. I bought a new one and I mounted it on the passenger side fender near the horn, it's a cooler spot than under the coolant overflow. no problems since.
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Unread 02-26-2008, 05:08 PM   #7
pat8942
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1992 YJ Wrangler 
 
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Quote:
Originally Posted by maximum729 View Post
I saw this thread and seen it was the exact problem i was having:

1990 YJ
I-6
4.2L (AMC 258)

Friday I took it out in the fields for a few hours in 4-low literally going 5MPH or less the entire time. Late that evening i was heading up the ditch to head home and It lost all it's power

The jeep would idol GREAT! and if i was in neutral (automatic) it would run fine also even if i reved it up. BUT as soon as i put it in gear and put a load on it (even in 4-low) it would run up to about 1500RPM then start sputtering backfiring. I though it may have been due to the extreme temp changes here in Minnesota so i put a bottle of seafoam in the tank and let it idol. The next morning i started it up and drove the 4 miles into town and it worked great again. As soon as i was coming home it started acting up by backfiring and poping just as it did the night before.

when i got home i let it idol while i was searching around under the hood for maybe some loose vacuum lines. and all of a sudden it just shut off as if i turned the key off... now I've got no spark.

I've replaced the
-pick up coil
-distributor cap
-had the ignition coil tested

Now i tore out the ICM. there is only one place in the area that can test it. they want $10 bucks just to test it... and everywhere in town that i can order it from wants $105-124 for it... If it's bad is there a good place to buy one online? Also, how is the best way about testing to make sure there isn't a short in the wiring?
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Unread 04-13-2008, 06:48 PM   #8
Unscathed
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2001 TJ Wrangler 
 
Join Date: Mar 2007
Location: Atlanta-Kennesaw
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Hey guys, I am having a similar problem with my 4cyl 95 YJ...

It seems my coil isn't getting any power.. it was running fine and all of a sudden it just cut out and when I tested the spark off the coil.. I wasn't getting any.. I replaced it as I figured I had to do it anyway.. and I already replaced the cap, rotor, plugs and wires a couple weeks ago..

Any thoughts?
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Unread 07-24-2010, 11:12 AM   #9
Ridgejeep
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1993 YJ Wrangler 
 
Join Date: Jun 2009
Location: Miami Florida
Posts: 36
i am having the same prob with my 4.0 93 and ive replaced everything but the icm maybe thats my next step i thought it mite be a rotten wire in the ing.
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Unread 09-20-2010, 07:07 PM   #10
ThomasYJ
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1993 YJ Wrangler 
 
Join Date: Dec 2008
Location: , All over
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My engine just started it the other day ive got a YJ 4.0. I just completed a fuel tank swap (cracked the original, got replacement from junk yard) and an alternator upgrade(from '98 dakota) since the original siezed as well. took it out the night of the swap to get fuel and it ran like a champ. the next morning i noticed a slight hesitation when pulling out quickly around 3k rpm. later that day it got horribly worse with sputtering and mild to severe backfiring. usually starts around 2k rpm and progresses into the 1k-2k rpm range, cant even touch higher rpm. Ive got relatively new MSD wires and rotor/cap with a screamin demon coil and direct hits spark plugs(all installed last christmas). just replaced fuel filter tonight and still no dice. input??
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Unread 09-20-2010, 07:45 PM   #11
Que89YJ
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1989 YJ Wrangler 
 
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Hey RidgeJeep and ThomasYJ. That thread is 2 years old and a totally different setup. Post up a new thread and we can definitely help you guys.
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Unread 06-08-2011, 06:21 PM   #12
Ambie88
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1991 YJ Wrangler 
 
Join Date: Jun 2011
Location: Clovis, Ca
Posts: 3
Help! I can't seem to locate my ignition module on my 91' wrangler. I've been on so many sites that say it should be on the fire wall but i haven't had any luck. My repair book isn't helpful either it just shows what the part looks like and says that it's near the battery. I even called the dealership all they could tell me is that it's in the distributor. Which i can't see how that is because the diagram does not show that part in there! Can someone please help!!!
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Unread 06-08-2011, 07:34 PM   #13
Que89YJ
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1989 YJ Wrangler 
 
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Ambie you should start a new thread for your issue. Welcome to the forum. Explain what's going on and I am sure we can help.
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Unread 06-09-2011, 08:20 AM   #14
Ambie88
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1991 YJ Wrangler 
 
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Location: Clovis, Ca
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The problem I'm having is the my jeep keeps shutting off on me while I'm in gear and just about every time this happens my brakes and steering locks! Before this happens my jeep putts while accelerating I know it's not my fuel system because I replaced all that last summer. I've taken it in three times when the problem first started a month ago they guessed it was the crankshaft sensor. I had them replace it when I got it back it drove fine for a day but the problem became worst to where it would shut off while idling. I was lucky that I ever got it home. Since then I replaced the throttle position sensor, map sensor and the spark plugs all myself. I've called a local jeep shop who said they came across this problem before and that it was the ignition module. I'm having a problem finding it's location my catalog shows what the part looks like and says it's near the battery on the fire wall. I'm able to locate the ignition coil but the wires just lead out to a mass of other wires that then lead to my pcm which I all so replaced last october.
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Unread 06-09-2011, 09:06 AM   #15
Que89YJ
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1989 YJ Wrangler 
 
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Ambie, post a new thread. The selection for a new thread is at the top left hand side of the main YJ forum page. http://www.jeepforum.com/forum/f12/ . Its a blue button that says new thread. Its probably not your ignition module (We call it an ECU on the forum). You need to post up the info you just did to a new thread and we can go from there. You should start by checking your fault codes.
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