Why does my 1988 Jaguar XJS V12 have no fast idle on cold start and idles high when warm?

- Verify throttle linkages for correct adjustment

- Check for vacuum leak

- Check/replace engine coolant temperature sensor

- Check/replace cold start thermo time switch

High Idle When Warm:

- Verify throttle linkages for correct adjustment

- Check for vacuum leak

- Check/replace idle speed control valve

- Check/replace throttle position sensor