jebmccall

my xj has been doing this for some time now.... i know should of looked at it sooner. alright my problem is that intermitently my 4.0 will stumble going back down to idle like when backing up and letting off the accelerator pedal, or creeping up to a stop sign. it will drop down to 200 rpms and then work its way up to normal idle after about 5 seconds. i have had it completely stall out a few times, very few.

i believe it did this before i did the engine swap also 1.5 yrs ago like i said its been a while. the jeep runs great down the road, just intermitently stumbles only with in the first five minutes of driving coming back down to an idle.

there are no vaccum leaks

parts that have been replaced not due to this issue neccesarily include

tuneup including high quality wires
champion copper plugs gap checked at .035
cap and rotor
throttle body has been cleaned
new tps
brand new header
new exhaust including catalytic converter
has newer battery and newer alternator
cam position sensor

grounds have been checked, all have good contact
battery voltage stays at 13.5-14volts unless the rpm drops way down causing the alternator not to spin fast enough to charge.
things that i am thinking may be the cause includes
map sensor
possible o2 sensor
crank position sensor
possible bad ecm???

cruiser54

Did you remove the throttle body, clean the IAC, and where it's pintle seats in the throttle body/

jebmccall

not sure what the pintle is, but yes i removed every sensor on the throttle body and cleaned.

PocketsEmpty

What brand TPS/CPS's did you get? It seems not too uncommon for non-Mopar TPS and CPS units to fail not long after replacing the original.

jebmccall

its a bwd unit, it was doing it long before, and after i replaced the sensor, i replaced the tps thinking that might of been what was causing torque converter issues. fixed the problem there

cruiser54

Pintle is the tip of the IAC. Did you clean the seat where it seals into the throttle body also?

jebmccall

would it be a good idea just to replace the iac since it is 17 yrs old and has 185k on it? money is not a huge concern.