OT - ZJ idle problem

[robselina]

Hi guys,
You guys are a wealth of knowlege on all things automotive so I thought I'd ask here in addition to the NACGA site. I'm 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! smile.gif

[Green Giant]

Try here for the little jeeps:
JeepsUnlimited (http://www.jeepsunlimited.com/)

[flatbackdragon]

also chk
www.e-toolbox.com/ads/index.cfm (http://www.e-toolbox.com/ads/index.cfm)
click your year, jeep, model, submodel, and service recalls etc, run thru the items to see what may be causing the problem.
My 94 ZJ trans is acting up due to colder weather, low temps below 30 will make these auto trans seem to be acting up but cold trans fluid the culprit. Warm the vehicle up B4 driving seems to help

Transfer case, id plate on rear of case, circular tag attached provides model, assembly and serial #'s along with low range ratio.

[illegalFSJ]

Some of the symptoms you list sound alot like fuel pump issues. I replace tons of fuel pumps for hard starting, dying problems on late-model vehicles.

[flatbackdragon]

I've replaced fuel pump twice in last 2 years, 1st one gave out, 2nd the wife got clipped on left rear corner of bumper and drove for 2 blocks before it died. DCX service manager told me that it could still be good just not at this altitude, they have taken 'bad' fuel pumps from colo. and put them on vehicles at low altitudes and it worked fine. sounds crazy to me too...what ya gonna do, it's a 300$ pump! Don't, don't get a checker/autozone pump to replace with, use one from Chrysler, unless you like replacing it every year or less.
The hard starting/surging also could be caused by the ignition cables. Change the spark plug wires and route them as shown at the site I mentioned above, under service bulletins, Ignition, electronic ignition. There has been a problem with spark jumping thru coil wire, plug wires. Also may need to keep the plastic looms over wires as DCX did this to keep out heat and to prevent crossfiring thru wires. Has helped out on my 94.

[Rogue]

the only way you're gonna get this fixed right is to have scan tool hooked up and reading live data while the car is acting up - you give me a symptom i can give you at least 5 possible causes on a fuel injected vehicle - from your description it is possible a few of the problems are related - i would start with cleaning throttle body and idle air control, these jeeps are notorious for crank sensor probs ( hard start, erratic operation )

[robselina]

Originally posted by RogueStar:
the only way you're gonna get this fixed right is to have scan tool hooked up and reading live data while the car is acting up - you give me a symptom i can give you at least 5 possible causes on a fuel injected vehicle - from your description it is possible a few of the problems are related - i would start with cleaning throttle body and idle air control, these jeeps are notorious for crank sensor probs ( hard start, erratic operation )from what I'm gathering on the NAGCA site, you're dead on. I checked the engine codes, nothing in there, just code 55 that signals end of sequence. I cleaned the throttle body, replaced the PCV valve and TPS, since they were possible cuprits. It seems that it's either the IAC or EGR at this point, I've got an IAC on order and I may just try removing the EGR and see if that fixes it if the IAC doesn't. TPS and IAC seem to be tempramental from what I'm gathering, so I'm hoping that the IAC will take care of it all.

Thanks for the suggestions guys,

[Rogue]

you can normally just give the IAC a thorough cleaning - the shaft gets carboned up and gets sticky and the end of the pintle gets carbon built up on the end of it so when the iac says im at this postion and the computer says well you're in the right postion ( which it isn't cause of the carbon build up)but the rpm isn't right the computer gets confused and starts changing the timing to control the rpm - i would do this before throwing a bunch of parts at it - can't say i've ever replaced many TPS on chryco - doesn't mean they don't go bad but...you're money