1998 3.0, v6. Manual Trans, A/C, approx 190thousand miles. When coming to a stop the engine actually increases RPM’s and runs at this increased RPM until I shut the engine off. When I restart engine still racing. It does this intermittentaly approx 50% of the time doesn’t matter if A/C is on/off. Have replaced O2 sensor, idle air control valve, EGR solenoid, and valve. Had the last done on 4/23 on 5/1 it was back to idling high. This has been a ongoing problem for about 5 years, replace items works for a short time and then back to the idling high.
Check the TPS (Throttle Position Sensor).
A loose or broken TPS can cause intermittent bursts of fuel into the injectors and and unstable idle because the PCM thinks the throttle is moving.
In addition to checking the TPS, has the throttle body ever been cleaned? The cable/return spring mechanism should also be inspected for binding/sticking