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Old 09-01-2013, 10:41 PM   #1
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Exclamation Cylinder 1 Mis fire

Hello to all,

I have read a whole lot of threads about mis fire but still am not sure what is causing mine. Here is what happens:

I have gotten 3 cylinder 1 mis fires (engine light comes on) but the engine runs fine and there is no noticeable change in engine performance. This has happened over the last month.

I have had my injectors cleaned and my spark plugs replaced with the right spark plugs. All 3 times that the engine light came on it was first thing in the morning when I first started the engine. As the engine started the engine light remained on. That is the ONLY way I knew there was a mis fire.

The gas is replaced often so it is not old gas. Any suggestions?

Thanks,
UtahRay

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Old 09-01-2013, 11:50 PM   #2
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Not sure what year u have but O2 sensor(s) would be a good place to start.

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Old 09-02-2013, 12:23 AM   #3
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Same symptoms before & after the new plugs? If so, my first suspicion would probably be the ignition coil rail.
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Old 09-02-2013, 09:59 AM   #4
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Thank you for the responses. Yes, Jerry same symptoms before and after. I was sort of leaning towards the ignition coil. I have a 2003 Jeep Wrangler Rubi. I guess it could be an 02 sensor but I would think I would get an 02 sensor readout on the computer wouldn't I?
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Old 09-02-2013, 10:06 AM   #5
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mine was a cracked intake manifold... It cracked while replacing the exhaust manifold.
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Old 09-02-2013, 10:20 AM   #6
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A bad 02 sensor won't always generate a CEL or DTC code... but I cant see a bad 02 sensor causing a single plug misfire either.
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Old 09-02-2013, 08:37 PM   #7
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Hey Jerry, I've been having the misfire in #1 too. Comes w rough idle n seems to over load on gas sometimes. I changed out my O2 sensor and that seemed to work. That was until the trip after ur post above. How often have you heard of the coil rail going bad? Is there a way to test it? Or should I just buy a new one. I hear they don't go out to often but I could be wrong. I've done O2((mopar), crank sensor, new plugs twice. Cleaned iac n TB out. It comes and goes. Somedays runs like a top others rough idling. Ur opinion please
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Old 09-02-2013, 09:24 PM   #8
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I think if it was a bad coil rail, you would have a misfire on both cylinders 1 and 6. Since the coil rail has three coil packs, each pack is used for the ignition of two cylinders. Per the shop manual, you can check the primary resistance on the coil rail. It should be 0.71 to 0.88 Ohms.

sm

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