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Unread 12-06-2012, 03:44 PM   #1
crazyjz
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1997 TJ Wrangler 
 
Join Date: Jul 2011
Location: Westminster, CO
Posts: 7
Cylinder 5 Misfire

I have a misfire on Cylinder 5 of my 97 jeep wrangler 4.0L Straight 6. I have replaced the distributor cap and rotor, i have replaced and gaped my sparkplugs i have tested the plug wires, i have done electrical testing on the wiring leading up to the fuel injectors, i even switched the fuel injectors from 5 to 3 and 3 to 5 but still i am getting a misfire on cylinder 5. my lack of knowledge and experience has me stuck, i dont know what else to do, other than take it to a mechanic, but i really would rather learn something new to try my self. does anybody have suggestions for a young new (jeeper?)
Thanks, Justin ZJ

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Unread 12-06-2012, 08:45 PM   #2
laybackman
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1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
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Quote:
Originally Posted by crazyjz View Post
I have a misfire on Cylinder 5 of my 97 jeep wrangler 4.0L Straight 6. I have replaced the distributor cap and rotor, i have replaced and gaped my sparkplugs i have tested the plug wires, i have done electrical testing on the wiring leading up to the fuel injectors, i even switched the fuel injectors from 5 to 3 and 3 to 5 but still i am getting a misfire on cylinder 5. my lack of knowledge and experience has me stuck, i dont know what else to do, other than take it to a mechanic, but i really would rather learn something new to try my self. does anybody have suggestions for a young new (jeeper?)
Thanks, Justin ZJ
The ASD relay provides power to all the injectors on a dark green wire with a black stripe. The PCM provides a separate ground for the injectors to fire them. #5 probably isn't getting that ground. It should be a pink wire with a black stripe. Follow it back to where it goes into a splice...maybe the wire got broken.

It goes eventually goes back to pin B6 of the PCM plug (The white plug)
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Unread 12-07-2012, 11:36 AM   #3
crazyjz
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1997 TJ Wrangler 
 
Join Date: Jul 2011
Location: Westminster, CO
Posts: 7
Well yesterday I decided to try and re-replace just the number 5 spark plug, and now it is running like new.. I never thought to check the very first thing I replaced. Thank you laybackman for your reply I still will take a look at those wires, am just starting to learn about the detailed workings of my jeep and it will be nice to know about grounds and the like.
Thank you again,
Justin ZJ
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Unread 12-07-2012, 02:18 PM   #4
laybackman
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1995 YJ Wrangler 
 
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Quote:
Originally Posted by crazyjz View Post
Well yesterday I decided to try and re-replace just the number 5 spark plug, and now it is running like new.. I never thought to check the very first thing I replaced. Thank you laybackman for your reply I still will take a look at those wires, am just starting to learn about the detailed workings of my jeep and it will be nice to know about grounds and the like.
Thank you again,
Justin ZJ
Ok that is good to hear! But, here is how I think. Now that you replaced #5 cylinder spark plug with another new spark plug, was the plug NG or you tugging on wires and generally pushing stuff around that 'fixed' this problem?

I would get a multimeter and check the plug out.
Set it at the lowest Ohm setting and then check for resistance between the electrode and the sprak plug's threaded body. ANY resistance means the plug is NG.
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