Closed throttle valve switch controls injection quantity for idle, switches off injection during deceleration fuel shutoff and ignition point setting at idle. Open valve switch controls fuel quantity at full throttle.
Disconnect wiring lead from throttle valve switch. Install ohmmeter between terminals on wiring lead. Reading should show continuity at idle and full throttle position of throttle valve switch.
To check switching point, open and close throttle valve slowly. When ohmmeter indicates continuity at idle stop position, measure gap between idle stop and idle adjusting screw with feeler gauge. See Fig 1 .

Fig 1: Checking & Adjusting Throttle Valve Switch
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Gap should be .002-.004" (.05-.10 mm). Proper adjustment of throttle valve switch is important. Excessive gap will cause engine surge when throttled slightly.
Insufficient gap causes cold engine to stall at full throttle acceleration and warm engine will have no deceleration fuel shutoff. If gap requires adjustment, see THROTTLE VALVE SWITCH ADJUSTMENT under ADJUSTMENTS in this section.

CAUTION: DO NOT perform following test unless plug is disconnected from ECU.

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.

Safety Warning

Throttle Valve Switch: Function