Cylinder 1 Misfire on 1999 6cyl Sahara - Jeep Wrangler Forum

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Old 12-11-2010, 01:44 PM   #1
JDaviesspy's Avatar
Join Date: Dec 2010
Location: North Florida
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Cylinder 1 Misfire on 1999 6cyl Sahara

I have a 1999 Sahara 6cyl and I intermittently have the check engine light come on and code reads "Cylinder 1 misfire". When this happens the engine runs a tad rough, but not very bad. The rough idle passes and the code can be cleared usually within a hour. Engine runs very smooth and I have great throttle response.I have replaced the plugs, wires, cap, and even put in upgraded fuel injectors (Precision Injectors), but I still get the code 2 or 3 times a month, Is it the cam/crank shaft sensor??? If it was a cylinder issue is would not be intermittent...right?

In advance, your input and assistance is appreciated!

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Old 12-11-2010, 02:32 PM   #2
Knows a couple things...

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Join Date: Nov 2005
Location: Escondido, Calif.
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That sounds like the notorious misfire caused by a bad set of weak valve springs some early TJ 4.0L engines received. My '97 TJ had the same issue. I fought that issue for years before the factory addressed the issue with a TSB. The TSB basically just says to replace the valve springs with new valve springs which uses the same p/n, they are just updated, and to clean the combustion chambers with Mopar CCC (combustion chamber cleaner).

When you have a choice, buy American.

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Old 12-11-2010, 02:56 PM   #3
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Thanks Jerry! I had seen the TSB during my search, but was hoping it was something else and an easier and less expensive fix. Looks like I will have to bite the bullet! I appreciate your quick response. Thanks!!!
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Old 12-11-2010, 03:29 PM   #4
Join Date: Sep 2010
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I just fixxed that very same thing on my '97 TJ. New valve springs, "Deglazed" the valves with H2o, New spark plugs after . All is gooood now !

PS: A big "THANK YOU" to Jerry for all the info !
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