Excessive Fast Idle

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1990 Volkswagen Vanagon, 1990 Volkswagen Jetta, 1990 Volkswagen Golf, 1990 Volkswagen GTI, and 1990 Volkswagen Fox. However, it is still accessible from the selected car via links, so may be relevant.

Inspect accelerator pedal and cable for worn parts or binding.
Test idle switch (if equipped).
Test auxiliary air regulator and replace if necessary (if equipped).
Inspect throttle valve and adjust or replace as required.
Check carbon canister solenoid valves (CIS-E Motronic).
Test idle boost valve system operation (1.8L 8-valve engine only). Replace faulty parts as necessary.
Test coolant temperature sensor and wiring (Digifant II). Repair or replace as required.
Check throttle cable adjustment.
Verify vacuum hose routing is correct.
Ensure there are no vacuum leaks.
Check idle stabilizer operation (if equipped).
Ensure fuel system pressure and volume are correct.
Check auxiliary air by-pass regulator.
Check cold start valve for leaking (engine warm).