I am having a issue with my 99 cherokee. It starts right up idles good you take off and when you stop at a stop sign or light it idles rough runs good when you are driving it has new plugs, wires, cap, rotor, 784 injectors, running premium fuel with seafoam have no idea NO CODES are popping up the plugs all look good not wet and nice and tan any ideas?

 

Make sure it transmissio is tight I had mine come loose and it did some funky crap every now and then at idle and take off

 

Get 87 not premium

 

no help?

 

Rough idle can be caused by a few things, one of them being the IAC, which regulates air inflow during, well, idling. This IAC tends to build up some crud over the years, and then the pinion (or whatever that 'rod' is that goes in and out) might get stuck, causing the egine to run rough at idle alone.
If you havent cleaned it, this might be a good time (also to get it off the list). Write ups can be found on forum.
Let us know how you go. It might fix it, otherwise unto the next cause.

 

I cleaned the IAC and its housing, the throttle body the jeep has 231000 miles on it and it looks like a original iac is there anyway to test it for proper function i also sprayed brake cleaner all over the intake for a vaccum leak and nothing

 

Do you have to add coolant on occasion?

 

no i dont have to add coolant no smoke nothing going to check the spark flow and see maybe I have a bad wire or something. They are brand new but that dont mean anything

 

and my display says I am getting 20.3 combined fuel milage?

 

Well that's good. Better leave it alone.

 

I know it runs great when you are driving just at a idle?

 

Do a compression test, with those miles could be a wiped cam lobe.