My jeep cheroke 1998 4.0

This one sounds like a faulty throttle position sensor. If the computer has generated codes to indicate this, P0122 or P0123, start with a visual inspection of the wiring and connectors at the TPS which is located on the throttle body. Disconnect the wiring connector and look for any damage to the terminals. Reconnect the the wiring connector and use a scan tool to verify that the voltage changes smoothly from 1.0 V at closed throttle to 4.5 V at wide open throttle. If the voltage change is erratic or jumpy, try replacing the throttle position sensor. Sometimes, just disconnecting and reconnecting the wiring can solve a poor connection.