Hi guys,
Having a little issue with our 95 ZJ. It's the Limited model, so it got the 5.2L engine, 46RH tranny and the full time 4wd transfer case (anyone know the model #?) It's got 140K miles on the odometer and about 20k since we rebuilt the trans.
Anyway, when you come to a stop light, the Jeep will drop below normal idle after a few seconds and want to stall. Initially it only did this in Drive, but now it's taken to doing this in Park too. I thought it may be the torque converter, but now i'm thinking it may be a compound problem with more things wrong. The tranny was rebuilt 20k miles ago (though only a couple of months, we drive a lot) and it did this before and after the rebuild. I've also noticed a little "slack" in the drivetrain, and I'll get a little thud when I let of the gas sometimes in the 25-30MPH range. It almost seems like the torque converter is locked.
Last two symptoms it's experiencing are somewhat hard starting, it needs to be turned over more than I think it should when cold and also it will sort of "drag" sometimes when you hit the gas. If you let off the gas you get a little surge and then it goes back to normal.
These issues are all intermittent, and don't seem highly related to vehicle temperature in the case of the idle problem and "slack". The later two seem to hapen more when the engine is cold.
Anyway, sorry for the long post and thanks in advance for any help! :grin:
Rob

the model for the full time 4wd transfer case is 249. my jeep would drop below normal idle and then it would stall when i was stopped similar to your problem. try cleaning the idle air control with some throttle body cleaner. i cleaned the throttle body while i was at it and it seemed to fix the problem. good luck

If you let off the gas you get a little surge and then it goes back to normal.

that sounds more like your tranny cable needing adjustment. Mine did that a little and I took the slack out of the cable and it seems to be good. As far as the idling, have you checked the IAC motor? Its located in the throttle body. They sometimes get gunked up, etc etc. Ive heard that sometimes you can clean them, but generally you want to replace it. $70 or so? try Kolak? My friend has this problem and this solved it for him. Im idling lower and lower and I think I will try this as well. Good Luck.

PS. search for "IAC" and I you should find some more info on it.

thanks for the info and quick response guys. I'll try cleaning up the throttle body and IAC first thing in the morning. Is that air sensor pretty delicate or is it pretty robust? I'm wondering if I can go at the general area with a tooth brush and cleaner or if I'm going to cause harm doing that....

after searching around for idle air control problems, I checked my engine codes, only got a 55, so no problem there. Check engine light did come on shortly after the trans rebuild (couple of months ago), and it was supposed to be the EGR valve, however the light has never come on since and I never did anything about it since it didn't afect drivability. Thought I'd mention it incase it matters, since I'm seeing a corolation between bad EGRs and 02 sensors due to clogged catalytic converters. I do have a small exhaust leak aswell BTW.
After that it seems like TPS, CPS, O2’s and the PCV would be likely culprits right? can the EGR valve cause the idle problem if it isn't opening/closing properly?

when you take out the IAC make sure you dont push the plunger in while cleaning it.

tps . this did it to me twice. when you give it gas its fine but when you idle its not. check that as well. nothing major. about 60 bucks for a new sensor for the tps. if your facing the engine its to the right of the throttlebody.

well, i cleaned out the throttle body, replaced the air cleaner since it was dirty and replaced the PCV valve since it was OEM and didn't inspire confidence. Runs a little better, but still has the idle problem. I replaced the TPS and ordered the IAC. The TPS made it run a little better too, and I think it got rid of the surging problem I described, but still have idle problem. I should have the IAC by Monday, so I'll have to wait and see if that clears it up. If that's not it, I'll check again for vacuum leaks and try the EGR I guess.
Thanks guys,
Rob