- Start the engine. Then let it idle.
NOTE: Engine coolant temperature must be below 65°C (149°F).
- Remove the vacuum hose (A) from the intake air duct and connect a vacuum pump/gauge (B) to the hose.
- Raise and lower the engine speed and make sure the vacuum gauge reading changes as the engine speed changes.
If the vacuum reading does not change, check for these problems:
- Misrouted, leaking, broken, or clogged intake air bypass control system vacuum lines.
- A cracked or damage intake air bypass control thermal valve.
- Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
- Raise and lower the engine speed, and make sure the vacuum gauge reading does not change as the rpm changes.
If the vacuum reading changes, check for these problems:
- Misrouted, leaking, broken, or clogged intake air bypass control system vacuum lines.
- A cracked or damaged intake air bypass control thermal valve.