first of all it's not clogged I already checked that.
I think it is because my engine is running REALLY lean. I don't have an air fuel ratio meter so I can't verfiy that.

Does any one have any ideas or suggestions?

a little history. I have a 94 YJ that I just put a 98 TJ engine with a 94 XJ computer and harness in. the exhaust is ran down the drivers side to make room for the Dana 300. that is about all I can think of that would make any difference.

Any suggestions?

First Off Your A Newbie So Here is the Obligatory :flipoff2:

OK

I was just researching this cause i was going to put a 97 TJ motor into my 89 2.5L YJ.

From what many people has told me it is the CAM that is/will cause all the problems.

Here are some good explanations why via different forums:

As you'll see, the cam profiles are pretty different!

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=33113
and
http://forums.jeepsunlimited.com/ubb/Forum37/HTML/003899.html

Might be, might not be.

Maybe try getting the TJ EFI and Computer too???

back when cats were a new thing, you'd hear storys of them setting off grass fires. They do get pretty hot. With the newer ones, I think you might be right on the too lean idea, it'll sure make your motor run hotter, but with the computer controlled fuel management it shuoldn't be a prob. Maybe you'll need to do what Mangler suggestedabout the TJ comp.

Sounds like you are running rich to me.. You put a 98 engine into a 94 which fuel rail did you use?? which fuel pump did you use?? The 94 fuel rail has a return line to the tank with a pressure regulator The 98 has the pressure regulator built into the pump in the tank.. If you used the 98 fuel rail with the 94 pump you are over pressuring the system which causes too much fuel to be injected therefore it is running rich and unburned fuel is passing to the cat causing it to overheat. It will not be long before you need to replace it..

maybe u live next door to a neuclear waste dump and your cat has been pooping in the neighbors yard....... or it could be what cutter said

Originally posted by Cutter
back when cats were a new thing, you'd hear storys of them setting off grass fires. They do get pretty hot. With the newer ones, I think you might be right on the too lean idea, it'll sure make your motor run hotter, but with the computer controlled fuel management it shuoldn't be a prob. Maybe you'll need to do what Mangler suggestedabout the TJ comp.

oh yea should have told that too. I am using the fuel rale from the 98, so there is no regulator. I am using the tank and pump from the 94 so there is no regulator in there either. I solved this problem by putting in an adjustable fuel regulator. it is hooked up just like the regultor would be on the 94 fuel rail. it is running 42 PSI which is what the FSM said to run for a 98 motor.

Any other suggestions?

Originally posted by hy_desert_4wheeler
Sounds like you are running rich to me.

Exactly what I was thinking. I had a CJ-5 that started missing one night at a campout (one of the spark plugs wasn't sparkin') we were on our way back to camp anyway so I just drove the mile or so into camp. When I got out, the Cat was glowing red. Having unburned fuel hit the cat will definitely heat it up.

- Mike

Got a 81 Scrambler w/151CID engne, sitting in my yard, that runs rich/burns lots of oil, and when the cat was on it, it glowed cherry red.;)

HTH.

MJ

I'm jelious. I wanna glowing CAT too, so i can see what 's wrong underneath at night. :cry

Sounds like a rich mixture to me too (but I'm a newbie so what do I know :D ). Anyway your dumping unburned fuel into an already hot cat. Try leaning out the mix, should fix right up.

switch to the fuel rail that your computer is suposed to work with! this is the easy/safe solution. You could tune the fuel pressure yourself but without a dyno or emisions testing equipment I don't see how you could get it just right.

it's running fat, not lean........

had a Dodge d-50 that ran like that till the carb got a rebuild...

and dodge even had a re-call for the cat!

cool, and no more cherry red monster...




--Sherpa

touch it and let us know what color your finger is

When this happened to me, it was actually because of a bad O2 sensor. :confused: bad signal to the brain, ran to rich.

Tell her to see a doctor and get some ointment for that thing....and whatever you do DONT TOUCH IT !:eek:

ok guys I figured it out. turned out to be an easy fix.

I replaced the MAP, ran new vacuum hoses and that did not do a thing.

checked other stuff to and nothing

started pulling injector wires to see if I could hear a difference....nothing

started pulling plugs and when I pulled the 6th wire (last one of course) there wasn't a change, every other time it would make themiss worse. checked the spark on the wire and it was good so I pulled the plug.

the gap on the plug wasn't even enough to fit a piece of paper in there. I guess when I was changing the plugs during the engine swap I must have hit it on the head or the walls and flattened it out. any regapped it and it ran beautifully.

NO MORE HOT KITTY EITHER!!!


it is always the stupidiest things that is the last thing to look for until you find it and wonder why you didn't check it first.

what was happeneing is the gas wasn't getting used for that cyl and it was just dumping it straight into the exhaust. and the cat was doing it's job by trying to burn it up. and it was doing a lot of buring too!!!

any way I am happier now