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Old 11-22-2012, 12:41 AM   #1
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Engine Misfire - Rough Startup - Possible Causes?

Back in the summer, the jeep would have a hard time starting up for its first time of the day, sometimes It would crank and crank until finally started up. (I changed the crank sensor before this problem occured so that is out of question)

Now, within the past few months when I go to start it after I had just ran it, didnt even had to have been for long, when I restart it will Idle Rough and Studder, eventually fixing itself after a minute or so.

When I drive it on long trips at high speed I have noticed that the check engine light will turn on with a misfire code. I have had a different cyl code each time.

Things I have changed and checked:
Spark Plugs changed 2 months ago - OE Champion
Crankshaft Sensor 3 months ago - Standard
Ignition Coil - Did not change but checked each coil resistance and it is at Haynes manual specs

What I think it might be?
Fuel Pump/Module
Fuel Injectors
IAC or TPS?
Maybe Ignition Coil?

Any ideas please let me know!!

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Old 11-22-2012, 12:48 AM   #2
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Hook a fuel pressure gauge to the schrader valve on the fuel rail. You can rent them from some part stores like autozone. If nothing else you'll at least eliminate a FP problem.

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Old 04-10-2013, 02:57 PM   #3
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Hey catnip. Did you ever figure out your misfire problem and shifting problems on your jeep Thanks
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Old 04-10-2013, 05:37 PM   #4
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I had a similar issue a while back..... What I found it to be was the ignition leads to the plugs. The rubber had degraded, and upon very close inspection, I saw that it was arcing out to the block, at roughly the same time as it threw up the codes. It was only on taking them off and inspecting thoroughly I found cracks in the rubber around the contact. Changed the leads, problem went away.
Hope this helps.

Darren
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Old 04-12-2013, 01:13 PM   #5
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Quote:
Originally Posted by DarrenT View Post
I had a similar issue a while back..... What I found it to be was the ignition leads to the plugs. The rubber had degraded, and upon very close inspection, I saw that it was arcing out to the block, at roughly the same time as it threw up the codes. It was only on taking them off and inspecting thoroughly I found cracks in the rubber around the contact. Changed the leads, problem went away.
Hope this helps.

Darren
Strange issue there, are you talking about the rubber boots connected to the ignition coil being worn or mounted sideways? When I did spark plugs awhile back I changed the boots as well so I don't think it would be that but I'll inspect it.
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Old 04-12-2013, 01:15 PM   #6
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Sounds exactly like a bad (leaky) fuel pressure regulator to me.
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Old 04-12-2013, 01:16 PM   #7
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Quote:
Originally Posted by Drdetail66 View Post
Hey catnip. Did you ever figure out your misfire problem and shifting problems on your jeep Thanks
I did somewhat, I changed the fuel pump assembly a few months ago with a carter cause the fuel pressure was very low and it seemed to help quite a bit. If you are having the same issues as I was, check your fuel pressure with a tester from auto zone..

However, the problem still comes back every once and a great while, I know my o2's need replacing and I planned on doing both pre o2's soon. I'm sure that will clear it all up

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