Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here XJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.

Free Run Misfire

Old 04-27-2013, 07:06 PM
  #1  
Newbie
Thread Starter
 
Join Date: Apr 2013
Posts: 11
Likes: 0
Received 0 Likes on 0 Posts
Model: Cherokee
Default Free Run Misfire

I have an 86 Jeep Wagoneer with the straight 4.0 6 cyl engine, Renix electronic system, Auto Trans. It has a free run miss. While driving up hill under acceleration, it runs fine. Going downhill under deceleration, it runs fine. When you move the throttle between acceleration and deceleration, it will misfire, itís a jerking uneven misfire and does the same thing between deceleration and acceleration and does the same jerking misfire when youíre on level road and just trying to hold an even speed. It also does it when taking off from a standstill if you take off in a normal matter. You can take off like youíre on a drag strip and it doesnít miss. Another thing Iíve noticed lately is that when you let off the throttle and coasting to a stop, you can hear the engine surging up and down in RPM, no miss but just the surging. Iíve worked with the throttle position sensor some but it doesnít seem to make any difference and all the plugs, wires , cap etc are in good condition. Any help is greatly appreciated.
jlmclean is offline  
Old 04-27-2013, 09:34 PM
  #2  
CF Veteran
 
Join Date: Oct 2011
Location: cameron MO, Bakersfield CA
Posts: 1,265
Likes: 0
Received 0 Likes on 0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
Default

Go to Cruisers' tips in the info threads, or to Cruisers' page, he has alot of Renix tips there to start.
highmileage is offline  
Old 04-27-2013, 10:16 PM
  #3  
::CF Moderator::
 
cruiser54's Avatar
 
Join Date: Aug 2011
Location: Prescott, Az
Posts: 37,895
Likes: 0
Received 1 Like on 1 Post
Year: 1990
Model: Comanche
Engine: 4.0
Default

Originally Posted by highmileage View Post
Go to Cruisers' tips in the info threads, or to Cruisers' page, he has alot of Renix tips there to start.

https://www.cherokeeforum.com/f51/cr...x-tips-153657/
cruiser54 is offline  
Old 04-28-2013, 10:58 PM
  #4  
Newbie
Thread Starter
 
Join Date: Apr 2013
Posts: 11
Likes: 0
Received 0 Likes on 0 Posts
Model: Cherokee
Default


Thanks for the replies. I had a typo, itís an Ď88 instead ofan Ď86. Cruiser, Iím glad you replied to my post. Youíre the reason I found theCherokee Forum. I have used the Jeep Forum some but found this one when someonehad posted a link to your tips. First, thanks for putting so many helpful and ďGOODĒtips out there for Jeep owners, GREAT JOB. You covered some of the areas Iíve questionedfor some time. Let me give a few more details about my misfire. I replaced myoriginal engine with a low mileage engine out of a wreck. It had a brokenintake so I basically used all my Renix components on the replacement engine.From day one after the swap, It would have a random miss on take off for thefirst couple times youíd stop and take off in the mornings. Since I had most ofthe sensors, Iíve switched some of them, installed new injectors, I did cleanthe two ground wires but didnít upgrade them, replaced the CPS with a MOPARreplacement, tested all the sensors (according to the test in the manuals) andnumerous other things but never got that little miss out of it. Occasionally, Iívegot it to the point it wouldnít miss for a couple days but it has always cameback. I finally just gave up and drove it like that for the last couple years.Seemed like if youíd warm it up a few minutes before youíd leave out with it inthe mornings, it didnít miss that bad or even at all. It has gotten worse overtime and is now getting to the point it aggravates you to drive it. Iím goingto do most of the tips you have posted and hopefully one of them will cure theproblem. My question is, if you were working on it, which one would you dofirst and in what order?
jlmclean is offline  
Old 04-28-2013, 11:02 PM
  #5  
::CF Moderator::
 
cruiser54's Avatar
 
Join Date: Aug 2011
Location: Prescott, Az
Posts: 37,895
Likes: 0
Received 1 Like on 1 Post
Year: 1990
Model: Comanche
Engine: 4.0
Default

Originally Posted by jlmclean View Post
Thanks for the replies. I had a typo, itís an Ď88 instead ofan Ď86. Cruiser, Iím glad you replied to my post. Youíre the reason I found theCherokee Forum. I have used the Jeep Forum some but found this one when someonehad posted a link to your tips. First, thanks for putting so many helpful and ďGOODĒtips out there for Jeep owners, GREAT JOB. You covered some of the areas Iíve questionedfor some time. Let me give a few more details about my misfire. I replaced myoriginal engine with a low mileage engine out of a wreck. It had a brokenintake so I basically used all my Renix components on the replacement engine.From day one after the swap, It would have a random miss on take off for thefirst couple times youíd stop and take off in the mornings. Since I had most ofthe sensors, Iíve switched some of them, installed new injectors, I did cleanthe two ground wires but didnít upgrade them, replaced the CPS with a MOPARreplacement, tested all the sensors (according to the test in the manuals) andnumerous other things but never got that little miss out of it. Occasionally, Iívegot it to the point it wouldnít miss for a couple days but it has always cameback. I finally just gave up and drove it like that for the last couple years.Seemed like if youíd warm it up a few minutes before youíd leave out with it inthe mornings, it didnít miss that bad or even at all. It has gotten worse overtime and is now getting to the point it aggravates you to drive it. Iím goingto do most of the tips you have posted and hopefully one of them will cure theproblem. My question is, if you were working on it, which one would you dofirst and in what order?
They're already prioritized for your convenience. 1 through 8. And 13.

Have you ever sprayed carb cleaner along your intake to head mating surface? If you used an HO intake/exhaust gakset instead of a REnix one, you can get a vacuum leak there.

WE will figure this out.

Check your CPS wire routing while you're poking around.

Last edited by cruiser54; 04-28-2013 at 11:11 PM.
cruiser54 is offline  
Old 04-28-2013, 11:12 PM
  #6  
::CF Moderator::
 
cruiser54's Avatar
 
Join Date: Aug 2011
Location: Prescott, Az
Posts: 37,895
Likes: 0
Received 1 Like on 1 Post
Year: 1990
Model: Comanche
Engine: 4.0
Default

Here's a diagram of the CPS wire routing.
Attached Thumbnails Free Run Misfire-cps-location.jpg  
cruiser54 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Expedition_XJ
Cherokee Chat
25
05-24-2018 11:40 AM
96Co
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
10
02-08-2018 03:51 PM
australian_expat
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
4
09-02-2015 09:02 PM
Jicki Rough
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
1
09-02-2015 09:36 AM
TNXJsleeper
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
1
09-02-2015 05:31 AM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Quick Reply: Free Run Misfire


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description: