Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1990 Audi 100 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Idle Switch
NOTE:
Idle switch terminal identifications are located on switch.
- Remove throttle body. Insert 0.004" (0.1mm) feeler gauge between throttle valve stop and adjusting screw. Connect ohmmeter between terminals 1 and 2 of idle switch. Loosen idle switch assembly mounting screws.
- Turn idle switch clockwise as far as possible. Slowly turn counterclockwise until ohmmeter indicates 0 ohms (continuity). Retighten mounting screws and repeat measurement. If resistance value is not obtained, replace idle switch and adjust.
- If resistance value is obtained, connect ohmmeter between terminals 2 and 3 of idle switch. Reading should be infinite (open). With throttle fully open, reading should be 0 ohms (continuity). If resistance value is not obtained, replace idle switch.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.