My YJ is having problem with hesitation problem. (4.0L cherokee motor/Auto)
I hope you can give me an advice.



When engine is cold, jeep hesitates when accelerating or idling in neutral and can't pass more than 2K rpm. Also immediately after starting, jeep almost wants to stall in reverse or drive especially if I try to make hard turns.

When engine is warmed up, it gets better but only goes up to 4-5K.



There is no error code other than 12, 33, and 55.
I have done some search (apparently not enough) and changed following items.
Distributor cap and rotor, plug wire, and fuel filter.
The muffler guy looked at my cat when I installed a new muffler 2 month ago told me my cat is 50% good.

Do you guys have any recommendations of what should I do next?

Thanks.

Well, it sounds like it's not getting enough fuel.... Did you try replacing the fuel pump? And it could just be you got somthing in the fuel line.

Trying to help here, Also check make sure all vacum hoses are tight. This shouldent be causing your problem but it's always worth a check.

Is you tank rust bad? If so than you might be getting flakes of metel in your line and that's your problem.

JOJO; what do the "codes" mean? Have you tried to search using Google to determine what your issues are? What does "50%" Cat mean? One-half clogged? Clogged cat kills power. Restricting exhaust has same affect as closing-off throttle body. Also, codes are year-specific, so what year YJ are we talking?
"God helps those who help themselves"--meaning you get the best help when you do some of the foot work first (God, I love the internet:grinpimp:)--search, then ask. Oh, by the way, a Google search using "yj" +"code" +"55" got me a list of '91 YJ codes, and meanings; code 12 was not listed. But then, I don't know what year we're talking about here.

It is 94 YJ.
I think I need a fuel pressure test then replace cat.
I thought I can get by with 50% clogged cat but I guess not..

I didn't think they are related to my problem.

12 Memory Standby power lost (battery cable disconnected)
33 Air conditioning clutch relay circuit open or shorted
55 End of codes

Thanks.