Okay I've got one heck of a pickle. I'll give stats on my vehicle now so ya'll can think about it while I tell you whats wrong....

94 YJ
2.5L 58K miles
Auto tranny (TF904)
Stock axles with 4.56 gears and 33" tires

About a year or so, after long trips (going home to houston from corpus christi) averaging 3000-3500 RPMS on the highway, somtimes after an hour of driving, the RPMS would bop down a couple hundred every few seconds. Usually if I turned the motor off at the side of the highway it would be fine.

But the past couple months the probably has been coming severely worse. There were times when I would be able to go 45mph or get 3000 RPMS, it would reach 3000 and just drop down to 800-1000 RPMS, and start putting loud, not so loud as a backfire though. Those times I'd replace fuel filter, air filter, oil, cap & rotor, spark plugs, and wires, and I just replaced the O2 sensor. And it would run fine for about a month, then do it all over again.

Now it is really severe, it won't rev to 2000 RPMS, and when i try to get it up there, it'll drop down to 800-1000 RPMS. On the way home from work I could only go 15mph, and at the last stop light there was white smoke coming from the undercarriage, not the tailpipe.

Since this is my daily drive and I work full time, and school is about to start, I really need to fix this problem. I only have so much time to work on my jeep, so I can only do a few things a day.

What I'm asking is what should I check out next? Should I check the distributer? Should I do a compression test to see if oil is coming into my cylinder? Or could it possibly be the tranny, the torque convertor has stopped locking up about a year ago, but I had the fluid flushed about 10K miles ago. I have a hunch that it is ignition since in the past a tune up would fix it for a while. I just want to know what I should work on tommorow since I will have a day off, along with this weekend which I have off.

Oh, and also, it revs up fine in neutral.... WTF

Thank you so much in advance. I hope someone can help me. :(

Could your exhaust be plugged somewhere? Sounds kinda like what happened to me, at times, when it dropped, it flet like an anchor was thrown out. My cat converter exploded inside and filled the muffler. If thats it for you, you are lucky, 15 mph would have at least gotten me hoe, but mine just died

EDIT: Smoke came from the same place on mine when my prob happened

Originally posted by LordRatner
Could your exhaust be plugged somewhere? Sounds kinda like what happened to me, at times, when it dropped, it flet like an anchor was thrown out. My cat converter exploded inside and filled the muffler. If thats it for you, you are lucky, 15 mph would have at least gotten me hoe, but mine just died

EDIT: Smoke came from the same place on mine when my prob happened

Cat was replaced about a year ago with a lifetime warranty Meineke PIECE OF CRAP that never stays welded on. A big baller style Flowmaster was replaced at the same time as well. Although, when the cat went out the first time, it did similar things, just not as drastic. Also the cat made lots of noise when it went out, it's not rattling now. I also got a check engine light when it happened the first time, not getting any lights now. And diagnostic codes don't show anything.

test your fuel pressure in the fuel rail. Do you have a FSM (factory service manual)? If not,buy one it's a good investment. I kinda think that it sounds like a clogged cat myself. Take off the exhaust and run it without cat or muffler and see if that helps (it'll sound cool). Still having problems, I would check fuel delivery. Make sure that you're getting proper pressure on the rail (there is a little check valve, you can borrow a tool from Autozone). Fuel filter might be clogged. Smell the exhaust when this happens. Does it smell rich? Then you might have a spark issue, but I doubt it.

First step is pull the exhaust.

SeanP

U say the torque converter stoped locking up about a year ago? If this is so then your converter and trany is toast. The lockup in a converter takes alot of heat out of the trany,if it doesn't lockup the trany will overheat. Good way to test trany is to start engine hold on the brake and shift into drive,it should go right into gear,u should be able to feel it then hit neutral and then reverse. Give it some gas to when its in gear and on the brake see if wants to pull itself good,if not its fried.

Sounds like my old clogged cat too, pull the O2 sensor out and see if it opens up, if not, fuel system check, and make sure your distributor is clean and working. Go out and drive it, get it to run like shit with your foot to the floor, then shut it off and coast to a stop, pull the plugs and check condition.

fuel pump maybe. you have a cut off exhaust pipe? like no exit pipe? if so it heats the tank which heats the gas which heats the pump which stops the pump. my 5.0 did that sometimes before I put pipes out.

Clogged cat, fuel prob (pump, filter, clogged line?) are my two guesses. I had a similar problem only mine would die completely. Had a bad fuel pump in it.

okay, i'm about to work on the piece of crap. My first step is to take the exhaust off. If that doens't solve it. I will check the fuel pressure.

I know one time I looked up my VIN and it had a recall for the fuel sending unit.... but one time when I was at the Stealership they ran it and said there was no recalls. So maybe there is a problem with the sending unit.

I had the same thing with my 94 YJ auto. Replaced everything from the fuel system and ignition system, no dice. Finally changed the muffler, redid the exhaust piping and the 02 sensor. Started pumping in 93 octane and it's been great since. My guess is 02 sensor. Even though you just replaced it doesn't mean it can't be bad again :(

I got error code 51 saying it's lean.... i'm thinking it's fuel pump.

I still have my old O2 sensor.... should I put it back in and see what happends?

i think i will have to agree with BIGDUDE and the others, 92 YJ 5-speed, same prob but not quite 15mph maybe 17:rolleyes: , i bought a new O2 sensor and have never thought about it again, a wire might have come lose of got pulled off, just because it is a new sensor doesnt mean that it wont go bad again, i would consider that a $30 trial and error well spent and maybe 15 min. of work

Originally posted by IndianaBlake
I got error code 51 saying it's lean.... i'm thinking it's fuel pump.

I still have my old O2 sensor.... should I put it back in and see what happends?

It's lean because your O2 sensor is fawked.

If it was your fuel pump the thing would just quit. I've never heard of many fuel pumps sputtering because they are a constant supply pump and the pressure is regulated on the fuel rail. A fuel pump like those has always just died by my experience, or maybe gotten clogged, but clogged is an all the time problem. I went through all that junk too and like I said, turned out to be the O2. Mine was also running extremely lean and the exhaust pipes were about red hot :eek:

I yanked off the O2 sensor and let it run without it in the exhaust to see if the clog was cat.... still sputtered (sounded like a giant lawn mower too :D )

I put the old one back in, and it did the same thing. My ignition isn't adjustable, so tommorow i'll get a fuel pressure guage and check my fuel pressure from the throttle body and see what happends......

Only three days till school :eek: :eek:

I know this is old,

I am searching for a solution for the same issue on a 91 yj.

Blake what ever became of this?