'90 2.5 bucking / cutting out - JeepForum.com
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Unread 08-20-2013, 09:15 PM   #1
ken98k
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1974 CJ5 
 
Join Date: Sep 2010
Location: North Pole
Posts: 5
'90 2.5 bucking / cutting out

My 1990 2.5 yj accelerates and runs like a top going down the the road but when I try to maintain a slow speed like on a logging road it bucks and feels like it's cutting out. But just a touch of the gas peddal and it revs right up.

The best way I can describe it is try going 10 mph while intermittenly turning the key on and off. Any other time its great.

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Unread 08-21-2013, 05:53 AM   #2
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,444
Is there any difference when its cold and after it warms up?
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Unread 08-21-2013, 06:01 AM   #3
WDNewman
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1989 YJ Wrangler 
 
Join Date: Jun 2013
Location: Central Mississippi, Mississippi
Posts: 707
I had problems like this with my '89 2.5. Turns out two things were major instigators here. The timing chain was shot (154,000 miles) and the crankcase position sensor bolts had backed out and it was just barely hanging on. All the other sensors/lines were checked out and they were fine. Runs like a top now.
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Unread 08-21-2013, 09:07 AM   #4
ken98k
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1974 CJ5 
 
Join Date: Sep 2010
Location: North Pole
Posts: 5
Quote:
Originally Posted by WDNewman View Post
I had problems like this with my '89 2.5. Turns out two things were major instigators here. The timing chain was shot (154,000 miles) and the crankcase position sensor bolts had backed out and it was just barely hanging on. All the other sensors/lines were checked out and they were fine. Runs like a top now.
Where is the postion sensor located?
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Unread 08-21-2013, 11:24 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,444
Here is a link to download the service manual:
http://www.jeepforum.com/forum/f12/c...block-1400388/
The CPS is on the rear of the engine on the top of the bell housing. Difference hot and cold?
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Unread 08-22-2013, 09:01 PM   #6
ken98k
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1974 CJ5 
 
Join Date: Sep 2010
Location: North Pole
Posts: 5
Quote:
Originally Posted by Que89YJ View Post
Here is a link to download the service manual:
http://www.jeepforum.com/forum/f12/c...block-1400388/
The CPS is on the rear of the engine on the top of the bell housing. Difference hot and cold?
Engine temp doesn't seem to affect on the problem. I was just thinking, this jeep has a distributer, why would it need a crank postion sensor?
Thanks for the link.
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Unread 08-22-2013, 10:03 PM   #7
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,444
For the injector.
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Unread 08-23-2013, 05:34 AM   #8
WDNewman
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1989 YJ Wrangler 
 
Join Date: Jun 2013
Location: Central Mississippi, Mississippi
Posts: 707
The CPS is located on the back of the bell housing. Drivers side at about 10 O'clock. Two bolts hold it on.
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Unread 08-23-2013, 08:19 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
Posts: 14,444
Use the service manual and do the check and adjustments on the ISA,TPS,WOT and the fuel pressure.
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Unread 11-02-2013, 05:53 PM   #10
willawolfe
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1994 YJ Wrangler 
 
Join Date: Nov 2012
Posts: 106
Just solved similar problem with my yj. Was a physically damaged spark plug. If you have not had a tune up recently. Start with the basic and cheap stuff. Plugs cap rotor, maybe wires.
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Unread 11-03-2013, 07:41 PM   #11
mlcasey13
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1995 YJ Wrangler 
 
Join Date: Sep 2013
Location: Goldsboro, NC
Posts: 3
My 95 was doing the same thing. I replaced the capacitors on the computer per some instructions I found: here http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/

I know the symptoms don't agree with that thread but it fixed mine. Its worth taking the computer out and looking at the caps.
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