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Discussion Starter · #1 ·
Hey guys, my 94 2.5L used to just backfire in the cold weather... it wasn't much of a problem if I let the jeep warm up a couple minutes before driving. But on the way to work today(25min drive) in 65 degree weather, it started backfiring as I got off the interstate.. When it backfires, it seems to be coming from under the floorboard (at the headers?)

I lose power when it backfires so I usually let off the gas or shift it up a gear.

Any ideas?
 

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Sounds like it may be running lean. Could be injectors, pressure regulator. Could be a bad sensor like water temp etc.
 

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I am no expert by any means. Mine started backfiring intermittently, so I changed plugs, wires, cap, and rotor button. It fixed my problem and the parts I took off didn't look bad. Hope this helps
 

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Discussion Starter · #4 ·
I am no expert by any means. Mine started backfiring intermittently, so I changed plugs, wires, cap, and rotor button. It fixed my problem and the parts I took off didn't look bad. Hope this helps
thanks shanman, I'll have to take a look later this week. I got new wires and plugs. The rotor and cap look fine but it's probably due for a replacement
 

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Discussion Starter · #5 ·
I must add, it only does this in gear.. in neutral or with the clutch in, I can rev up with no issues.

It did it on the way home last night and worried me. Everything was good the first 20 mins of my drive but after 5 minutes on the interstate, I felt it bogging down around 2500 rpm and if I pushed the rpms past 2700, it would backfire.
 

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I am no expert by any means. Mine started backfiring intermittently, so I changed plugs, wires, cap, and rotor button. It fixed my problem and the parts I took off didn't look bad. Hope this helps
x-2.... 1st place to start is with a tune up. I assumed that you had done that but after re-reading the original post..I guess not. A bad plug will misfire under a load.
 

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Discussion Starter · #7 ·
Garyk said:
x-2.... 1st place to start is with a tune up. I assumed that you had done that but after re-reading the original post..I guess not. A bad plug will misfire under a load.
I've changed plugs and wires. Seafoamed the engine. Only thing that hasn't been changed is rotor
 

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I would try the rotor and cap too. If all that is new or fairly new then I would look sensors.
 

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Well being a 94 that rules out a carb being the problem. Mine was back firing when my crank sensor went out. I think it is a common problem. It would be worth looking into. They don't cost much, but I was told to get one from NAPA or Carquest due to inferior parts at other chains. Good luck
 

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Discussion Starter · #10 ·
Well being a 94 that rules out a carb being the problem. Mine was back firing when my crank sensor went out. I think it is a common problem. It would be worth looking into. They don't cost much, but I was told to get one from NAPA or Carquest due to inferior parts at other chains. Good luck
Well I am gonna check the rotor and cap tomorrow when I wake up. I don't have alot of money to throw in parts for the Jeep. If anyone is around the Raleigh/Durham, NC area and would like to help, lemme know!
 

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Well I am gonna check the rotor and cap tomorrow when I wake up. I don't have alot of money to throw in parts for the Jeep. If anyone is around the Raleigh/Durham, NC area and would like to help, lemme know!
I live in Dunn which is about 45 min from you depending on how you drive. :whistling:
The Crank position sensor is about $25.00, but if you could make it down this way I have a friend that worked for Jeep for 12 years and now has his own shop. He may be able ot answer questions over the phone to steer you in the right direction. Here is a link to my crank position sensor problem http://www.wranglerforum.com/f8/spit-sputter-pop-124957.html
 

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Mine did that and it had multiple broken or missing vacuum lines. Replaced all the cracked and dry rotted lines. Especially the one to the pressure regulator and it went away.
 
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