4.2 engine trouble - JeepForum.com
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post #1 of 7 Old 01-02-2015, 08:02 PM Thread Starter
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1987 YJ Wrangler 
Join Date: Jan 2015
Location: wauchula
Posts: 4
4.2 engine trouble

Before i start i researched a lot before posting this but can't seem to find an exact match to my problem.

The jeep is a 1987 4.2 with the stock carter carb.

Recently it has been having trouble idling and i know that a bad vacuum line is to blame. But the last few times i have driven the jeep the engine will shut off while Im driving down the road in gear. This happens not at idle but in higher RPMs. When this happens it is as if somebody kills the ignition switch and the engine looses spark. after the engine dies ill try to restart it and the engine will fire up for a split second and die immediately (this happens dozens of times till it finally stays running). After several failed attempts the engine will catch and stay running.

Im pretty sure this is not a fuel pump problem because i can smell the unburnt fuel passing through the engine. I was looking at attempting the Nutter bypass but before i attempted i was going to pick yalls brains first.

Thanks for yalls help

daltonfarr69 is offline  
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post #2 of 7 Old 01-02-2015, 09:10 PM
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
Posts: 18,083
A bad ICM can act like that.

86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #3 of 7 Old 01-02-2015, 09:18 PM
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1990 YJ Wrangler 
Join Date: Mar 2009
Location: fresno, ca.
Posts: 99
Had same problem. Replace icm
rshbutch is offline  
post #4 of 7 Old 01-02-2015, 09:24 PM
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1990 YJ Wrangler 
Join Date: Jun 2008
Location: st. louis
Posts: 2,116
ICM (ignition control module) is what was wrong with mine when it did that. Hard to test it because it is intermittent. You got to wait until it fails to test it.

Some people replace it with a chevy type from hei distributor.
dancytron is offline  
post #5 of 7 Old 01-02-2015, 10:10 PM Thread Starter
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1987 YJ Wrangler 
Join Date: Jan 2015
Location: wauchula
Posts: 4
cool thanks guys, i think ill go ahead and order a replacement.

daltonfarr69 is offline  
post #6 of 7 Old 01-02-2015, 10:12 PM
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1989 YJ Wrangler 
Join Date: Jun 2012
Location: Gulf Coast
Posts: 149
CRT HEI and never use that darn icm ever again
sardog211 is offline  
post #7 of 7 Old 01-03-2015, 04:28 AM
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1987 YJ Wrangler 
Join Date: Apr 2007
Location: west palm beach fl
Posts: 1,990
it could be a bad icm but when mine did that it was the ignition switch. X2 on the CRT HEI, save the money you would spend on a ICM and get the HEI distributor instead.

Do everything with a positive attitude, it won't always work but you'll piss enough people off to make it worthwhile.

the voices aren't real but they sure have good ideas.
roadyrob is offline  

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