I need help, I have a 1999 jeep cherokee with a three inch lift, its been having some throttle problems so i cleaned the IAC (Idle Air Control) and changed all the spark plugs. The engine is a strait V6 4.0L. I don't know what kind of tranny it has but it is automatic. I don't think thats the problem, I,m 16 so i don't know to much about cars but any advice will help
info: when i start the car it idles great but once I shift into drive and push on the gas, the car wont respond, but after a second the engine will jolt and kick in, this happens a few times until the car starts to run amazingly. This problem doesn't happen in reverse. If anyone has any advice on what to do it will help. I don't want to take it to the shop unless i really have to. I'm more of a hands on kind of person. Thanks for the help!

Is the tranny fluid showing full?
if it is does it look like motor oil and smell burnt? (should have a very light brown color with a red hue, or be pinkish to red.)
Is it slow on takeoff when tranny engages?
Does it do the same thing in 4hi?

I am having the same issue with my 99 Cherokee. Are you saying if the trans fuild is bad it will have this problem?

By the way. It's a I6. Not a V6

Am not sure why you call it an idle speed problem. Do you mean the transmission slips when put in drive? Lke you can hear/see the rpm's go up but the car doesn't move/speed up?
In that case start with checking the transmission fluid for level and quality.

If the engine stumbles when put into gear, thats likely another issue.
If you put your pedal down, and initially nothing happens, but then it kinda jumps forward, that again something different (like a faulty TPS e.g.)

Good advice for both of you guys here^^.

Pull the trans dipstick. Follow the instructions on it.

And do replace with dexron/Mercon III fluid

I know you guys are new, but you need to develop some good habits of vehicle ownership.

ALL lubricating fluids should be checked for level and condition at oil change time or when a vehicle is newly acquired, whichever comes first......

Fuild looks good I changed it about 60000 miles ago. Planned on changing soon anyways. I was planning on using synthetic.

Change it now. Dex/Merc is cheap and it only takes half hour to do a drain and fill.

Aisin Warner recommend only DM fluid in the aw4 transmission. At least make sure it's a DM synethic fluid.

If you really want to use a synthetic in an AW4 go with Valvoline MaxLife D/M or Castrol Transmax. Both are quality fluids that meet the friction modifier requirements of the AW4.

Do not let any parts store fools tell you otherwise. They usually say ATF+4, which causes exactly these problems.

Normally I'm all for synthetic fluids but ATF is kind of a pain since the drain-n-fill process is ineffecient and wasteful. Go for it if you want but don't expect it to be cheap (unless you do a complete fluid exchange, which is covered elsewhere)

Ok now onto the technical side of the matter. Why does bad trans fluid cause a rough idle?

Doesn't...

Check your tps and iac on throttle body, refresh all ground connections