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Unread 10-29-2011, 11:11 AM   #1
JeepJon15
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88 4.2 YJ Ignition Module questions

I've been skimming through lots of forums and it seems i have a bad ignition module. I wanted to post my symptoms before i go pick one up and see if the wise people here on jeepforum agree with me.

I will randomly have a rough time starting the jeep, which isnt the worst part.

Very randomly the jeep will turn off while i'm driving. Sometimes ill be going 50 mph and be able to start it back up immediately if i pop it in neutral while im still rolling. Sometimes it will take 5-15 minutes of the car sitting for it to start. Sometimes I get frustrated and kill the battery trying to start it back up.

When this happens the lights still stay on, i dont have a radio so i cant say anything about it. And if i remember correctly my gauges all bottom out.

Cap and plugs are fairly new, its nuttered and my timing is around 8-10 tbc.

Yesterday morning it wouldnt start no matter what i did so i had to grab a ride to work. And this morning i went out and it fired right up. Its quite inconsistant, Earlier in the week i went 4 or 5 days with no problems after replacing the air filter. And on a side note the fuel filter seems fine, it passes air with no problem.

Sorry if i rambled on... ill be messing with it today and tomorrow so any help would be awesome. Thanks guys

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Unread 10-30-2011, 10:01 AM   #2
JeepJon15
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Anyone lurking around who knows about this?
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Unread 10-30-2011, 10:12 AM   #3
raynmaker
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Sounds about right. When you change it move it up from under the washer fluid bottle. You might look at the stealth hei mod. Gm coil and ign modual with team rush is awesome.
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Unread 10-30-2011, 10:27 AM   #4
JeepJon15
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Thats a good idea. How would you recommend making room for it up there?

I wanted to add; I started it up a little while ago after it sat for most of yesterday and it shut off after running for about 5 min. I increased the timing slightly to 10-12 ish just to see what happened. It then shut off after say... 15 min. Does this raise any flags other than the ignition module? Maybe that's useless info...

Thanks for the response
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Unread 10-30-2011, 10:54 AM   #5
JeepJon15
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One more thing i thought of that may or may not be connected. Sometimes when i turn the key to start the jeep it seems like theres a power surge where it turns very slowly then speeds up and fires up. As its struggling my lights typically dim a bit then get full power back between engine turns. The starter is only about a year old, maybe a little less. Battery i think is from 04, but can a battery cause shut off problems? It does seem to die rather quickly when trying to get her started on bad days.
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Unread 11-06-2011, 07:36 PM   #6
JeepJon15
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Bump....

I was side tracked and just got to workin on the old "88 again over the weekend. I took the ignition module to autozone to have it tested; first of all the wires on mine had to be connected backwards from what the tester instructions were telling the autozone worker. Maybe because i have a Canadian model? Anyway, it tested fine after we got it hooked up right, and we tried a few times.

I dont know where to go from here with it. The ignition module is fine but it still shuts off after being on for about 15 min. Its hard to start. And the idle is a bit fluttery while it is running.

Any suggestion on where to go from here? Could the icm be going bad in phases and show up fine untill its hot or something then just **** out? Please any input will help. Im tunnel visioned now on ignition system so i re soldered all my nutter connections while i was at it.

Thanks for your time... help please!
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Unread 11-06-2011, 08:15 PM   #7
jhumphrey
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Quote:
Originally Posted by JeepJon15
Bump....

I was side tracked and just got to workin on the old "88 again over the weekend. I took the ignition module to autozone to have it tested; first of all the wires on mine had to be connected backwards from what the tester instructions were telling the autozone worker. Maybe because i have a Canadian model? Anyway, it tested fine after we got it hooked up right, and we tried a few times.

I dont know where to go from here with it. The ignition module is fine but it still shuts off after being on for about 15 min. Its hard to start. And the idle is a bit fluttery while it is running.

Any suggestion on where to go from here? Could the icm be going bad in phases and show up fine untill its hot or something then just **** out? Please any input will help. Im tunnel visioned now on ignition system so i re soldered all my nutter connections while i was at it.

Thanks for your time... help please!
You're ICM is bad. They will test fine 9/10 times. Get a new one and be done.

Side note. If you want to test it, redneck style, get some compressed air. When it shuts off, spray the ICM with the air (the ICM will frost up). It'll start right up. I also read you can smack the ICM with a big hammer when it shuts off. Never tried it.
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Unread 11-06-2011, 08:32 PM   #8
Old4X
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Have you added a dedicated ground to the ignition circuit? The black wire (3 wire harness) coming out of the distributor is the ground for the ICM. Splice a good, solid ground into this wire and see if your problems persist. If so, then try another ICM.

The stealth HEI mod is cheap and gives better performance than the Duraspark ICM you now have. This would be a better replacement.
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Unread 11-06-2011, 09:54 PM   #9
timatoe
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Quote:
Originally Posted by Old4X View Post
The stealth HEI mod is cheap and gives better performance than the Duraspark ICM you now have. This would be a better replacement.
+1
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Unread 11-07-2011, 06:22 AM   #10
roadyrob
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if your jeep is nuttered the icm no longer functions, my WAG would be coil breaking down or as stated bad ground. I would install a HEI, you will be very happy with the results.
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Unread 11-07-2011, 06:58 AM   #11
Old4X
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Quote:
Originally Posted by roadyrob View Post
if your jeep is nuttered the icm no longer functions, my WAG would be coil breaking down or as stated bad ground. I would install a HEI, you will be very happy with the results.
Nuttered or not, it has to have a functioning ICM (ignition control module) in order to even start, it is what takes the place of the breaker points in the dizzy. (you may be thinking of the emission computer under the glove box).

Even the self contained HEI dizzy has an ICM, it lives under the dizzy cap in a very hot and electronically hostile environment. Take that same internal module, remote mount it to a quality heat sink, and you have an excellent ICM that is internally voltage regulated (no resistor needed), and provides the hottest spark from 200 RPMs to 6,000 RPMs.

Nothing wrong with the stock dizzy or coil for 4.2 operating speed range. The Team Rush mod just uses the latest and bigger dizzy cap to cut down on cross firing, and really should be on all our 4.2 dizzys.
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Unread 11-07-2011, 07:16 AM   #12
raynmaker
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If your wires were crossed i wouldn't trust it even if it 'tested' good. They have circut boards in them that crack and when bumped or heated or cooled even just a deg will cause issues.

Either go with gm mod or get new icm. Mount it on top of the fender close to the horn. If you have no room there find a place on the fire wall or somewhere high and dry and maybe a little cooler.

http://www.junkyardgenius.com/ignition/jeep/HEI01.html
This with the team rush is one of the best upgrades you can do. Don't forget the gm coil it is the key to the extra power.
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Unread 11-07-2011, 11:10 AM   #13
timatoe
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Quote:
Originally Posted by roadyrob View Post
if your jeep is nuttered the icm no longer functions, my WAG would be coil breaking down or as stated bad ground. I would install a HEI, you will be very happy with the results.
Not true, the Nutter Bypass eliminates the ECM not the ICM.
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Unread 11-07-2011, 12:55 PM   #14
roadyrob
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sorry for the wrong advice, mine was discoed when I got the HEI.
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Unread 11-08-2011, 06:59 AM   #15
JeepJon15
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Awesome thanks a lot everyone. I'm going to look into/do the HEI mod as long as its in my budget for the week. I've been grabbing rides to/from work, and i think its wearing thin on my friends lol, so i need to figure this out asap.

Now if i'm correct the Team Rush upgrade is a little more pricey? I guess it depends what all you can find at the junk yard. But is the HEI alone gunna help if i dont upgrade everything else right away?

Thanks again guys, Jon.



PS. Just to make sure; does everyone concur that the ignition module will test fine most times even if it is bad? Is this just because of the heat that is introduced to make it turn off?
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