I researched this issue on the net to no avail. Individuals with the same issues reported having problems in the following areas.

1. Spark Plugs - Need Replacment
2. Vacumm Leak - Identify leak - Replace Hoses
3. Throttle Housing / Intake - Carbon Build Up - Needs Cleaning.
4. Oxygen Sensor - Needs Replacement
5. Air Flow Sensor - Needs Replacement
6. Cylinder Firing Order / Cam Adjustment

* Rent an ECU reader and see if you get codes.

Sorry, Others may have more experience with this...

2002 4dr Kia Sportage 4X4
Tires:235/75/15, Wheels: Black 15x8 Steel ProComp 2.5" B.S., Hubs:Warn Manual, Lift:3" UPYOURKIA, Trailer Hitch, Cargo Rack, Clinometer.