LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Volkswagen >> 1987 >> Vanagon Base, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (BOSCH Cis-E System) >> Testing >> Electrical Components >> Idle Speed Boost Valves
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Idle Speed Boost Valves

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1987 Volkswagen Scirocco, 1987 Volkswagen Quantum, 1987 Volkswagen Jetta, 1987 Volkswagen Golf, and 1987 Volkswagen GTI. However, it is still accessible from the selected car via links, so may be relevant.
  1. To test boost valve No. I, engine oil temperature must be at 176°F (80°C) minimum. If equipped, A/C system must be off. Run engine at idle speed. Turn on all electrical units except A/C system. Turn in idle speed adjusting screw to lower idle. At 750 RPM, boost valve No. I should open and idle speed will increase.
  2. Pinch shut outlet air hose after "T" connector. Engine speed should drop. Leaving air hose pinched shut, raise engine idle speed to 870-930 RPM. Open air hose. Idle speed should increase. When 1050 RPM is reached, boost valve No. I should close and engine speed should drop to 870-930 RPM.
  3. To check boost valve No. II (A/C equipped only), ensure A/C is off. Run engine at idle speed and pinch outlet air hose shut. Engine speed should not change. When A/C is switched on with air hose pinched shut, idle speed should drop.
scientia non olet · About LEMON Manuals