Idle Speed Boost Valves

Idle speed boost valves are used on 4-cylinder models. Vehicles without A/C use only 1 valve, called Idle Speed Boost Valve I. Vehicles with A/C also use second valve, called Idle Speed Boost Valve II.

With ignition on, constant voltage is supplied to idle speed boost valve I. If engine speed drops below 700 RPM, idle speed boost control (on relay board) completes ground circuit for boost valve I. Above 1050 RPM, control unit shuts off ground circuit to boost valve I.

Idle speed boost valve II is always grounded. When A/C is turned on, voltage is supplied to boost valve II.