Throttle Body: Testing and Inspection

NOTE: These checks are to be performed with the engine coolant temperature at 80-95°C (176-205°F).

EGR VALVE CONTROL VACUUM CHECK

EGR Control Vacuum Source:

1. Disconnect the vacuum hose from the throttle body exhaust gas recirculation vacuum fitting and connect a hand vacuum pump to the fitting.

EGR Port Vacuum Curve:

2. Start the engine and check to see that, after increasing the engine speed, vacuum raises proportionate to engine speed.

PURGE PORT VACUUM CHECK

EGR Control Vacuum Source:

1. Disconnect the vacuum hose from the throttle body purge hose fitting and connect a hand vacuum pump to the fitting.

Purge Hose Vacuum Source:

2. Start the engine and check to see that, after increasing the engine speed, vacuum remains fairly constant.

NOTE: If there is a problem with the changes in vacuum in either test, it is probable that the throttle body requires cleaning. Refer to SERVICE AND REPAIR

For diagnosis and testing of the idle switch, throttle position sensor and the idle speed control servo, refer to COMPUTERIZED ENGINE CONTROLS.