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Unread 11-23-2015, 11:55 PM   #1
CkC99
Junior Member
1994 YJ Wrangler 
 
Join Date: Nov 2015
Location: Caliente, Nevada
Posts: 14
94 YJ Running Rough

I purchased a 94 YJ with a 2.5L for my son. The jeep has 108,000 miles on it so my son and I decided to give the jeep a full service. When we purchased the Jeep it ran good except for an exhaust leak. I purchased the Crown full exhaust system since the pipes were rusty. We replaced the spark plugs (auto lite gapped at .035). Purchased new spark plug wires, new distributor cap and rotor, new serpentine belt, and a whole lot of other parts. After replacing all the above, I started the jeep and now it's running rough and a little rich.

I checked the exhaust to see if there were any leaks and couldn't find any. I then put the old plugs back in and still running rough. I then put the old wires on as well as the distributor cap and rotor and still running rough. I double checked the spark plug wires to make sure they were in the correct firing order. I also checked the rotor to make sure it was seated properly. The new distributor cap and rotor are still in good shape.

When I pulled the old plugs on it when I first purchased it and they were burning clean. Now the new plugs are black but dry.

My check engine light isn't on. I tried the OBD ignition trick and the only codes it shows is the battery was disconnected and no ac. I have had nothing but problems installing the exhaust system but I don't think it's the cause of the problem.

The only thing I can think of now is o2 sensors which are ordered. Is there anything else I can check?

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Unread 11-24-2015, 12:54 AM   #2
manvstaco
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1992 YJ Wrangler 
 
Join Date: Nov 2015
Location: port orchard, washington
Posts: 73
Did you verify the timing didn't get adjusted by accident? Sounds silly but it's possible.
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Unread 11-24-2015, 06:29 AM   #3
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 19,930
If it is an O2 sensor issue it would run fine until it gets warm and goes into closed loop. If there is no difference cold/warm it probably isn't the O2 sensor. The exhaust manifold would be the same thing. Intake manifold leak would give you a higher idle. My bet is that the intake air temp sensor or the coolant temp sensors are not connected. Try doing a battery disconnect for 10 sec. to reset the ecu. Also, strongly recommend you do the cleaning of the IAC and throttlebody as part of your tune up. Look on youtube for instruction vids. Also here is a link for the factory service manual. Download it. Cant get better info then the Manual or the peeps here. Welcome to the forum. You might want to bookmark his vids. Great info there too.

http://www.youtube.com/watch?v=bsLQSA5L5B8
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Unread 11-24-2015, 07:50 AM   #4
Jeeps2006
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1991 YJ Wrangler 
 
Join Date: Nov 2011
Location: Poulsbo, WA
Posts: 89
Could need a new coil.
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Unread 11-24-2015, 09:26 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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I just question if it was running good before the tune up. Then I would be suspicious of something that was done. You know what I mean Jeeps. Coil is a good call though.
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Unread 11-24-2015, 09:38 AM   #6
skullcandy77
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1993 YJ Wrangler 
 
Join Date: Jan 2015
Location: Atlantic city, new jersey
Posts: 95
Just some ideas and questions. Was it running good before you put the new pieces on?. Did you check and see if your injectors are clogged? Is the alternator whining or loud? You should check the fuel rail pressure and see if you have a vacuum leak.
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Unread 11-24-2015, 10:23 AM   #7
SailerMatt
Make it work
1995 YJ Wrangler 
 
Join Date: Dec 2014
Location: Vallejo, CA
Posts: 107
Welcome to the Forum!

You can go ahead and check your O2 sensors if you want. Here's a link on how to do it: http://www.youtube.com/watch?v=NKsS6AELPuM

Additionally, I'd go around and make sure you didn't accidentally knock a vacuum line out. Really easy to do as they get older and looser.

Does it idle rough, but smooth out with power? Or is it just consistently rough? If so, it could be as simple as a spark plug wire not pushed in all the way...

Let us know what you find!
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Unread 11-24-2015, 10:32 PM   #8
CkC99
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1994 YJ Wrangler 
 
Join Date: Nov 2015
Location: Caliente, Nevada
Posts: 14
Thanks for all the info.. I have to agree it has to be something I did but I'm just not finding it. It idles rough when it's cold or hot and runs rough with power or at idle. I have tried some of the advice you guys have given me and still the same results. I tried bench testing the o2 sensor and (A) it's bad or (B) operator error. When I did the heat test it would not get close to 1 volt but did drop temperature rapidly. I already ordered the o2 sensor before I posted this so it's going to get replaced either way.

I disconnected the battery to rest the ecu. I checked the intake air temp sensor and the coolant temp sensor and both are connected. I ordered these today.

I quadruple checked the spark plug wires to make sure they are connected which they were. I also pulled each spark plug wire while it was running to see if there were any changes which there was on all 4 cylinders. I also checked the vacuum lines, visually, and could not see or hear any signs of leaking. I'm new to jeeps so I'm looking up a vacuum line diagram just to make sure I didn't miss anything.

I did notice that there is an exhaust leak coming from the manifold and the front exhaust pipe. . This exhaust system has been nothing but a pain from day one. If I can get it running right, I'm definitely taking it to a muffler shop and having it replaced. I also noticed that it is still running rich as well. I also checked the tightness of my serpentine belt with a gauge and it was loose. I don't think the belt would have anything to do with it but at least throw that out there. The belt isn't squealing and the alternator isn't making any noise either.

I have not checked to see if the injectors are clogged just because the motor was running fine until I did all these changes. I haven't checked the timing yet either. I will let you guys know the outcome when i have replaced the sensors.
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Unread 11-25-2015, 04:04 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 19,930
Quote:
Originally Posted by CkC99 View Post
Thanks for all the info.. I have to agree it has to be something I did but I'm just not finding it. It idles rough when it's cold or hot and runs rough with power or at idle. I have tried some of the advice you guys have given me and still the same results. I tried bench testing the o2 sensor and (A) it's bad or (B) operator error. When I did the heat test it would not get close to 1 volt but did drop temperature rapidly. I already ordered the o2 sensor before I posted this so it's going to get replaced either way.

I disconnected the battery to rest the ecu. I checked the intake air temp sensor and the coolant temp sensor and both are connected. I ordered these today.

I quadruple checked the spark plug wires to make sure they are connected which they were. I also pulled each spark plug wire while it was running to see if there were any changes which there was on all 4 cylinders. I also checked the vacuum lines, visually, and could not see or hear any signs of leaking. I'm new to jeeps so I'm looking up a vacuum line diagram just to make sure I didn't miss anything.

I did notice that there is an exhaust leak coming from the manifold and the front exhaust pipe. . This exhaust system has been nothing but a pain from day one. If I can get it running right, I'm definitely taking it to a muffler shop and having it replaced. I also noticed that it is still running rich as well. I also checked the tightness of my serpentine belt with a gauge and it was loose. I don't think the belt would have anything to do with it but at least throw that out there. The belt isn't squealing and the alternator isn't making any noise either.

I have not checked to see if the injectors are clogged just because the motor was running fine until I did all these changes. I haven't checked the timing yet either. I will let you guys know the outcome when i have replaced the sensors.
Does it seem to be idling high? Use a can of carbon cleaner and spray around the engine and listen for and change in idle. Manifold especially.
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Unread 11-27-2015, 07:45 PM   #10
CkC99
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1994 YJ Wrangler 
 
Join Date: Nov 2015
Location: Caliente, Nevada
Posts: 14
Update..... I replaced the o2 sensor, air temp sensor, map sensor, coil, fuel filter, one vacuum line, and fixed the exhaust leak at the manifold and front pipe and still was running rough. I quadruple checked the spark plug wires, distributor cap and rotor and all was still good. I pulled the spark plugs and they were fouled up. I changed the plugs and it's running good!!!! I hope I got it figured out. I'm still planning on replacing the exhaust by a professional.
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Unread 11-28-2015, 11:18 AM   #11
SailerMatt
Make it work
1995 YJ Wrangler 
 
Join Date: Dec 2014
Location: Vallejo, CA
Posts: 107
Should've checked back sooner. I had the same issue. Bought these platinum plugs and they just didn't work well. Went back to good ole copper and it runs like a champ.

Glad to hear it's all good. Talk about a tune up with all the parts put into your jeep!
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Unread 11-28-2015, 08:45 PM   #12
CkC99
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1994 YJ Wrangler 
 
Join Date: Nov 2015
Location: Caliente, Nevada
Posts: 14
Quote:
Originally Posted by SailerMatt View Post
Glad to hear it's all good. Talk about a tune up with all the parts put into your jeep!
No kidding.... All that's left is a radiator flush, which I will do when it warms up, and then the motor is done!
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