1997 TJ Wrangler 4.0. Misfire codes - JeepForum.com
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Unread 08-14-2011, 07:29 PM   #1
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1997 TJ Wrangler 
Join Date: Aug 2011
Location: Surprise, Arizona
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1997 TJ Wrangler 4.0. Misfire codes

Check engine light on, codes for multiple miss fires. I replaced the Spark plugs with OEM copper tops, replaced the spark plug wires with Bosch wires, replaced the Cap and Rotor, Had injectors cleaned and checked, I guess i can order the Jeep OEM plug wires but do not know what else to do!
It seems to idle and run great!

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Unread 08-15-2011, 03:00 PM   #2
Jonny Jeep
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1997 TJ Wrangler 
Join Date: Feb 2007
Location: Manchester, UK
Posts: 5,230
Welcome to the forum. Bad batteries or connections can cause all sorts of problems on Jeeps. Charge the battery up using a proper charger and get it load tested to make sure it isn't the battery causing the problems. Also remove and clean up the battery connectors and terminals so they are bright before refitting. Hopefully it's something simple like that.
Online factory service manuals and parts lists - http://www.jeep4x4center.com/knowledge-base/index.htm
If it doesn't work properly, look for the service manual link at the bottom of the page.
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Unread 08-15-2011, 03:10 PM   #3
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1998 TJ Wrangler 
Join Date: Apr 2004
Location: , Southeast MI
Posts: 25,714
Did you clear the codes after doing all the work?
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Unread 08-15-2011, 06:31 PM   #4
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1998 TJ Wrangler 
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Location: Edgerton, Wisconsin
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Like he said, clear the codes. Drive it for a while and recheck if you need.
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Unread 08-15-2011, 07:23 PM   #5
Jerry Bransford
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2004 TJ Wrangler 
Join Date: Jan 2003
Location: Escondido, California, California
Posts: 62,976
'97 and early '98 had some bad batches of valve springs installed which will eventually cause multiple '43' codes which are the misfire codes. No amount of ignition component changing will help with this particular issue. The fix is to replace the valve springs and, possibly, a valve job if the misfires were ongoing long enough.

The factory issued a TSB (Technical Service Bulletin) for this issue and it basically just says replace the springs and clean the combustion chambers afterwards with Mopar CCC (combustion chamber cleaner). A TSB is not the same as a Recall so you'll get no $$$ assistance from the factory or dealer fixing this problem.
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