When my jeep is at idle in park, it is idle-ing very rough. When I go to put it in drive and accelerate, it hesitates and the rmp's bounce around and jolts me forward and back, unless I step on it hard. I replaced plugs, wires, cap and rotor and also cleaned the IAC, and still seem to be having issues. Gas mileage also seems to be worse than usual. Can anyone tell me what needs to be fixed/replaced?

 

I was having a similar rough idle and I had a filthy throttle body and IAC. Cleaned both of those and it has been good since. I would start with cleaning the throttle body since it's cheap and easy to do.

You can see how dirty it was here.

https://www.cherokeeforum.com/f2/rou...etimes-198067/

 

Check cruiser's tips.

I'd be looking into CCV tubes being clogged from the valve cover and around the airbox as well as checking grounds (dipstick tube) and maybe vacuum leaks.

Possibly o2 sensor but meh...I'd wait on that. You have a 99? Is it throwing any codes? How long has it been doing this?

 

Test the TPS and check fuel pressure at the fuel rail.

 

ok so I replaced the upstream 02 sensor the other day, and this morning I replaced the TPS. Still having the same issues... I occasionally get a popping sound from under the hood too. Nothing seems to help.

 

Did you check the fuel pressure?

 

i will go loan out a pressure tester tomorrow morning. What pressure should i be reading at idle?