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Unread 01-01-2014, 07:54 PM   #1
kromjeep
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1994 YJ Wrangler 
 
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Help Needed, '94 YJ losing engine power?

Driving on a 3 hour trip in 5th gear engine began to loose torque, so i pulled over to check, everything appeared fine. When i cranked it back up it drove fine for about 30 mins till it happened again. There was a very faint squeaking noise when pushing on the gas pedal.

When it lost speed it was a similar feeling as to running out of gas, but i had a full tank so thats not it. I also checked my oil and it said it was at safe level.

Please help?!

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Unread 01-01-2014, 08:30 PM   #2
NHfireLJ
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Clogged catalytic converter? Tranny fluid level?
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Unread 01-01-2014, 09:27 PM   #3
pete1991YJ
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Welcome to JeepForum, you have just found one of the best jeep sites anywhere!

It could be a number of things, so its a good idea to check the easy things first. This will give you a general area to inspect further.
One of the first things I do when I suspect engine troubles it to check the computer for error codes. Its easy and all you need is the ignition key. No special tools required. Here is a video that shows how:
I suggest you should do this first and post the codes. Hope that helps.
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Unread 01-02-2014, 06:33 PM   #4
kromjeep
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I did this and got 4 codes (12, 33, 17 and 55):

12: Memory Standby power lost (Battery or computer recently disconnected)
33: Air conditioning clutch relay circuit open or shorted ( Also will show up for rigs without AC)
17: Engine stays cold too long (bad thermostat)
55: End of codes

code 17 is the only one I'm not sure about?
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Unread 01-02-2014, 08:02 PM   #5
pete1991YJ
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Quote:
Originally Posted by kromjeep View Post
I did this and got 4 codes (12, 33, 17 and 55):

12: Memory Standby power lost (Battery or computer recently disconnected)
33: Air conditioning clutch relay circuit open or shorted ( Also will show up for rigs without AC)
17: Engine stays cold too long (bad thermostat)
55: End of codes

code 17 is the only one I'm not sure about?
The code 17 could be a bad thermostat *or* a bad coolant temp sensor. The temp sensor is important because the computer does not read the O2 sensor until the engine is up to 185 degrees. When it reads the O2 sensor, it uses that to trim the fuel. So, if it never reads the O2 then it will run like crap and suck way too much gas, possibly burning up the cat converter in the process. That is one possibility, either the thermostat or the temp sensor.

The thermostat should be a 195 degree unit, about $15 at any parts store. The temp sensor is best from the dealer, the aftermarket ones aren't good enough. Probably about $40.

Only other thing that seems to fit your prob maybe a fuel system prob - either a clogged fuel filter, or the pump is getting weak. I would try and fix the temperature stuff first tho, since you already know for a fact that something is wrong there.

Be sure to reset the computer after you do any work, all you have to do is disconnect the battery for a few seconds.

Hope this helps!
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Last edited by pete1991YJ; 01-02-2014 at 08:03 PM.. Reason: sp
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Unread 01-02-2014, 08:39 PM   #6
Que89YJ
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1989 YJ Wrangler 
 
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In a pinch try and disconnect it or the O2 sensor. It will throw the ecu into default if it is a bad sensor and should get you on the road again but will cost you $$ because the calibration will run rich until its fixed.
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Unread 01-03-2014, 02:18 AM   #7
wrangler4me
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Mine did that from time to time. Would lose power and felt sluggish. Then it wouldn’t run over 2500 rpm for awhile then would run fine. Changed the cat and never had the problem again… Just a thought.
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Unread 01-03-2014, 01:18 PM   #8
yj94ne
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Quote:
Originally Posted by pete1991YJ View Post
The temp sensor is important because the computer does not read the O2 sensor until the engine is up to 185 degrees.
This is not true. Where did you read this? You are in closed loop before 185*. I run a 180* t-stat and can guarantee I run in closed loop once the jeep is at operating temp.

http://www.jeepforum.com/forum/f12/w...4-0-a-1841210/
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Unread 01-03-2014, 03:39 PM   #9
Que89YJ
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The closed loop should happen at 185. I won't go back into the whole discussion. The fact is that it can't be verified. The normal operating range should be 185/200 for optimal performance. If you are running a 180 and you don't see any difference in your fuel economy then the tolerance might be good enough. The coolant temp sensor is more important because it won't be able to know the temp is sufficient to start using the o2. I am waiting to see if he was able to run with the sensor disconnected. I hope he post back.
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Unread 01-03-2014, 04:22 PM   #10
The_Goob
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Mine did this when a spark wire fouled up and cylinder was dumping fuel, which led into the catalytic converter. Do you smell sulfur smell?

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engine , highway , oil filter , Torque , YJ

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