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 Sudden miss
#837105
09/20/07 04:56 PM
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Joined: Sep 2007
Posts: 7
OP
Need a Spot
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99 Wrangler 4.0 Auto trans.
Running fine on the highway at 75 mph., then exited the highway and came to a stop. I noticed a rough idle, then check engine light came on. Scan showed cylinders 3&4 misfiring. I changed coil, plugs, plug wires, cap & rotor and nothing helped. You can pull the plug wires off of #3 & #4 while it is running and the rough idle does not change. And the sound of the motor does not change. Plugs are getting fire and cylinders are getting fuel. Injectors are fine.
Any ideas?
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 Re: Sudden miss
[Re: mustang123]
#837106
09/20/07 06:09 PM
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Joined: Oct 2003
Posts: 7,768
Web Wheeler
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I would be swapping the injectors with 1 & 2 to see if THEY were the problem. If not then a compression check is in order.. Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />
professional bovine relocation specialist
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Re: Sudden miss
[Re: BigJim]
#837107
09/20/07 09:42 PM
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Joined: Sep 2007
Posts: 7
OP
Need a Spot
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Just had the injectors checked this AM. Mechanic said they are all working well. They are doing a commpression check today.
Any reason why cylinders 3&4 would both start miss firing at the same exact time?
If commpression related, why the two cylinders that are next to each other?
I appreciate your insight.
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Re: Sudden miss
[Re: mustang123]
#837108
09/20/07 11:49 PM
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Joined: Oct 2003
Posts: 7,768
Web Wheeler
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Just a guess or two.. low coolant and 75mph might cause a hot spot in the engine that burnt valves or melted pistons? Low fuel pressure caused a LEAN condition that did the same? Or even an exhaust manifold leak could burn the valves.. Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
professional bovine relocation specialist
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Re: Sudden miss
[Re: mustang123]
#837109
09/21/07 12:32 AM
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Joined: Sep 2007
Posts: 5
Need a Spot
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I was having a problem just like that one and it turned out to just be my throttle body sensor. Im no expert but you could start by checking that.
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Re: Sudden miss
[Re: thurrsROB]
#837110
09/21/07 02:33 AM
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Joined: Jan 2007
Posts: 353
Mudrunner
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i had this same problem when my throttle position sensor was bad, only it didnt throw a misfire code, it threw the throttle position code
WHEN THE ROAD ENDS, THE FUN BEGINS
97 sahara, 4in skyjacker lift, 33in tires, borla header & catback, 10in subs
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Re: Sudden miss
[Re: BigJim]
#837111
09/21/07 02:59 AM
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Joined: Sep 2007
Posts: 7
OP
Need a Spot
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Thanks Big Jim,
Is it just a coincidence that the code is on side by side cylinders? That's the part that has me stumped.
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Re: Sudden miss
[Re: thurrsROB]
#837112
09/21/07 03:00 AM
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Joined: Sep 2007
Posts: 7
OP
Need a Spot
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I'm hoping for a sensor problem and not something worse.
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Re: Sudden miss
[Re: playinmud]
#837113
09/21/07 03:05 AM
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Joined: Sep 2007
Posts: 7
OP
Need a Spot
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The scan was done by a kid at Autozone...I don't know if that had something to do with it. I would think an auto shop scan would be a little more precise.
Thanks for your input
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Re: Sudden miss
[Re: mustang123]
#837114
09/22/07 04:10 AM
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Joined: Jan 2007
Posts: 353
Mudrunner
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most scanners now a days are easy as hell to use, you find the make model and year of the car and then you hit scan, then it comes up with the code number (P0---) and then the name of the code, its as simple as reading a screen
WHEN THE ROAD ENDS, THE FUN BEGINS
97 sahara, 4in skyjacker lift, 33in tires, borla header & catback, 10in subs
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