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Discussion Starter · #1 ·
I just got a 92 YJ 4.0L 5-speed with 166K miles on it. I have put about 400 miles on it so far.

It seemed to run fine at first. I have added a stock tailpipe to it. I have also put E10 in it, but I do not know if the previous owner did.

I am now noticing a miss. I don't notice it a idle, but notice it around 1500+ RPM.

Any ideas on what to check?

Thanks,

Steve
 

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I just got a 92 YJ 4.0L 5-speed with 166K miles on it. I have put about 400 miles on it so far.

It seemed to run fine at first. I have added a stock tailpipe to it. I have also put E10 in it, but I do not know if the previous owner did.

I am now noticing a miss. I don't notice it a idle, but notice it around 1500+ RPM.

Any ideas on what to check?

Thanks,

Steve
spark? usually they miss from a lack of energy (spark) at high rpm, or something associated with that. Side note...a joke that floats around about an "engine missing"-it's usually found under the hood. I had to do it.
 

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Discussion Starter · #3 ·
If I check for spark using just the wire lead against the frame, will it show/no show a spark there? Or is the problem at the spark plug itself?

What would cause this?

I told my wife a had a cylinder missing. She asked me where it was.
 

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If I check for spark using just the wire lead against the frame, will it show/no show a spark there? Or is the problem at the spark plug itself?

What would cause this?

I told my wife a had a cylinder missing. She asked me where it was.
I just unplug the spark plug (then re-attach the wires) then have a buddy crank it over and look for the spark. If no spark then trace it back to the distributor. If it died while running, i've read that the Crank case position sensor is a huge cause for that. I hope this helps in some way. Also, good joke. haha.
I once told my girlfriend to change the fluid in her horn, and she went out and looked.
 

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Discussion Starter · #5 ·
The miss seem constant, like its the same cylinder. The CPS would make sense. The Chiltons says to read the resistance across it for a diagnostic. Do you know if that's actually an effective test?
 

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The miss seem constant, like its the same cylinder. The CPS would make sense. The Chiltons says to read the resistance across it for a diagnostic. Do you know if that's actually an effective test?
It has to be some sort of electrical malfunction. I'm not too sure about a CPS test, from a lack of knowledge, sorry. There is someone on here I can point you to that is well informed on electrical and all things "Fubar". I'm sure he/other members that join in can give you more info.

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I will just try to put in my two cents and hopefully point you into a right direction. Good luck.
 

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If the spark wires are the original ones they might be bad. It´s always a good idea to replace old wires with new ones.
 

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I'm an idiot......
I read the topic and wondered how you bought a jeep and didn't realize there was no engine in it.


....neeeeed more coffee
 

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I'm an idiot......
I read the topic and wondered how you bought a jeep and didn't realize there was no engine in it.


....neeeeed more coffee
haha, that was me at 4 am last night too! :rofl:
 

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I'm an idiot......
I read the topic and wondered how you bought a jeep and didn't realize there was no engine in it.


....neeeeed more coffee
Same thing here, but it's 2pm so go figure. "What, he didn't check?!" lol.
 

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Discussion Starter · #12 ·
I went out tonight and I think my o2 sensor is bad. The Chiltons says there should be no resistance, but it reads some resistance. Would that cause a misfire?
 

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if a crank position sensor fails it will kill the vehicle as the computer has no reference as to what cylinder to fire next. The common cause with a cps is when the motor heats up the sensor would short out causing the motor to die. It won't kill just one cylinder. Same goes for an o2 sensor, since yours is a 92 you should only have upstream o2's which determine the air fuel ratio for the engine, here again a faulty o2 will not cause a miss under engine load on only one cylinder. If a o2 shorts to 5 volt reference it will usually choke out the engine as the computer will think the vehicle is running to rich and will lean it to death. My guess would be to do a ignition tune up, cap rotor wires plugs. What you are describing is a pretty common complaint at the shop I work for when people are having misfires under engine load. Sorry for the essay but figured I would help out!
 
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