Jeep Cherokee Sport 2.5 D

indicates that the idle circuit or system is not operating as designed .
could be a sensor fault
best have the fault codes read to find the area of the problem

all gears ok but drive, full power from engine to tires, 1,2,R
right? but not drive. drives acts as Neutral or weak.
did you do the stall test , in drive.
1000 rpm weak, engine
2000 rpm good
over that much is tranny slip.
tranny issues.
read the fsm. then the on car service, section

wrong tranny.
the TCM shifts based in this , so
take both tranny to any tranny shop
and say make best out of 2, many can.
you could look in both FSM and see what parts need change out.
CASINGS.
the day of simple swaps are over...
electronic shifter trans are complex. and today even more so.
with ESP, and ETC. far worse........

you should have (sorry) joined Top Jeep forum.
then asked what works. before the leap,,, not much.

you have to decide that the hood could get warped or blow up over the windshild

low power to what, wheels or electrics? (dim dash/head lamps?)
if wheels,
is this true in all gears.?
is car A/T ? auto tranny?, is car 4wd or AWD, or what? options
are you in 2WD, (two wheel drive?)

if the engine has low power in any A/T cas?
FSM steps. (under A/T on car diagnosis) yes, RTM.

we do the stall test. (point car in safe direction, dig?)
we set brakes hard (and and foot)
we select DRIVE (or 1s to REV, i do all 3,one by one. )
we then race motor with right foot for 5 seconds max.
we look at the tachometer, it will be like 2000 RPM (stop now)
is it like 1000 RPM then the engine is weak
if much over 2000 rpm the tranny is slipping and is not a weak engine
these numbers are generic, the FSM covers this. read it. RTM
read the manual or get help. there are only 2 ways.

if all this is alien to you, then take it in
any ASE shop can do this.

Keep this a secret. [ Right] Tip in 1/2 a liter of auto trans fluid into the fuel tank. This needs to be done only once a year. Don't let this out! LOL

Give a try by change your transmission/filters and Transfer case oil.

the fuel filter is inside the tank. clean the throttle body and disconnect the battery a few minutes. the IAC valve may be bad, or dirty.

is it diesel engine?if so chech ur heater plugs

Seems like you might have wet the no 1 injector sensor..(little black plastic thing with 2 wires) It sends a pulse back to ecu and if wet it,s no good....