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Unread 08-04-2011, 10:53 PM   #1
Sawicki4wd
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1989 YJ Wrangler 
 
Join Date: Jul 2011
Location: Chicopee, Mass
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Yj 2.5 running super rich

My 89tbi is running super rich. I changed the cat the 02 sensor did a oil change changed my fuel pump and my gas tank (was rotting out on me) and I swapped my tranny (all syncros were shot) all this in the past 2 weeks. And now it's running super rich like it's burning my eyes and I went from about 12-14 mpg to about 5-6 which is killing my wallet. Any advise. And I found a weird 3 tubed vacuum line that I have no idea where it is suppose to go. Looks like all the lines run to the canister.

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Unread 08-04-2011, 11:11 PM   #2
MJMPC
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Check your fuel pressure reg.
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Unread 08-05-2011, 07:16 AM   #3
1tuffyj
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Does that use a return line? If so check it. Had same problem a few yrs back n found my return line pinched above my tank. No return flow = hi pressure.
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Unread 08-05-2011, 10:10 AM   #4
Cibus
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1990 YJ Wrangler 
 
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Exhaust Manifold Leak? Air could be sucking in and telling the 02 sensor that its running lean forcing it to dump more fuel.
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Unread 08-05-2011, 01:48 PM   #5
Sawicki4wd
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I don't thinks it's a manifold leak. I'll check tho. I noticed the bad gas Mileage after I Swaped my tranny. I'm wondering if I forgot to hook something up or if I broke a wire. I did find a conector that ran to my tranny that had 4 wires going to the conector and 4 coming out but only 2 go somewhere. The other 2 are just hanging there. And I also found a vacuum line that was hooked to anything on either side.
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Unread 08-06-2011, 01:47 AM   #6
Sawicki4wd
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1989 YJ Wrangler 
 
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Checked everywhere with starting fluid. No revs. Did find a sensor unplugged and a vacuum harness disconnected. It's running a little better but still really really rich. Any other advise.
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Unread 08-09-2011, 03:36 PM   #7
Sawicki4wd
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1989 YJ Wrangler 
 
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Well it's still running rich and I can't figure out why. I tried a new 02 sensor. Same problem. I'm getting exhaust in my cabin when I turn in off and out from under the hood. Could and exhaust leak cause the richness
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Unread 08-09-2011, 08:44 PM   #8
Castr8r
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I just had that problem and my siuation was that the vacuum line to the MAT sensor had disappeared- gone, vanished! Found a piece of 1/8" vac. hose and forced it on- problem solved. I hope this helps yours. With all the lines hangin' loose you've got, I'd suggest that you buy a Chilton's Manual and start replaceing/hooking up vacuum lines.
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Unread 08-10-2011, 05:27 AM   #9
Alfons
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Cibus suggested looking for an exhaust leak - the starting fluid spray is a check for an intake or vacuum leak. Toasted exhaust valves will also give you the same rich running condition, but will usually be combined with backfiring through the throttle body.

A leak in the exhaust system between the cylinder and the oxygen sensor will give you sensor readings equivalent to a lean condition - the ecu sees this and increases the fuel flow to compensate.

I would check on the fuel pressure and the vacuum connection to the regulator - no vacuum at the regulator will raise the fuel pressure by around 8 psi, giving rise to a mild rich condition if everything else is in good shape. I think you have a combination of things giving you this problem, but the fumes from the engine bay would give me cause to look at the exhaust manifold and exhaust pipe connections first. If there are noticeable fumes coming from the engine bay, there should be enough of a leak that you should be able to see, and even feel where the exhaust is coming from.
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Unread 08-10-2011, 09:45 AM   #10
Que89YJ
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1989 YJ Wrangler 
 
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The exhaust leak in front of the O2 sensor makes it think its running lean. That is bad news because the computer will start dumping fuel. Its common to 1) crack the exhaust manifold especially near the collector tubes 2) loose/break the manifold bolts especially on rear near the firewall 3) burn or break the O2 sensor wire.
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Unread 08-10-2011, 06:47 PM   #11
Sawicki4wd
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Well what leads me to think the manifold is it happened after I Swaped my tranny. So I'm hoping it's an easy fix
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Unread 08-10-2011, 07:10 PM   #12
Cibus
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Its for a different engine then yours but the idea is the same.

http://www.jeepforum.com/forum/f12/h...ifold-1063245/
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Unread 08-11-2011, 12:43 PM   #13
Sawicki4wd
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Thanks. As soon as I get back from the beach I'll get on swapping it
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Unread 08-30-2011, 12:31 AM   #14
Sawicki4wd
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Well today I finally finished Playing with my jeep. I went for the simple ole swap the exhaust manifold. Haha yeah right was a pretty big job. I got a new manifold an gasket. The tear down took me maybe 2 hours. Well it took me about 12 hours putting it back together. First of all who ever designed those damn manifold bolt locations needs to be shot. I had such a hard time getting all of the bolts to thread. I ended up cutting the egr tube off and making a block of plate so I could install the exhaust manifold first. Well once I did that it went a little bit smoother. Until I finished up and it would start. I couldn't figure out what I did. Turns out I so how disconnected my starter relay. Well I did all of that and replaced the 02sensor. And it's still running rich. I did have a crack In my manifold. Oh and FYI that colored engine paint. Does not hold up on the exhaust manifold. Haha figured that while it was off I might as well make it look nice.
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Unread 08-30-2011, 04:14 AM   #15
Que89YJ
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Did you reset the ecu by disconnecting the battery?
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