Throttle Body: Testing and Inspection

1. Testing the injection mixer involves testing each of the mixer vacuum ports to ensure proper operation, and that no vacuum passages or ports are clogged.

Fuel Injection Mixer:

2. Disconnect the vacuum hose from the injection mixer port D (Distributor vacuum), and connect a hand vacuum pump to the nipple.
3. START and race the engine and observe the vacuum reading at port D. The vacuum should increase with the engine speed. If the vacuum does not increase or increases erratically, clean the injection mixer vacuum port and retest. Reconnect the vacuum hose to port D.
4. Disconnect the vacuum hose from the injection mixer port E (EGR control vacuum), and connect the hand vacuum pump to port E.
5. START and race the engine, and observe the vacuum reading at port E. The vacuum should increase gradually with engine speed. If no vacuum increase is observed, clean the injection mixer vacuum port and retest. Reconnect the vacuum hose to port E.
6. Disconnect the vacuum hose from port M (Secondary air control vacuum) of the injection mixer, and connect the hand vacuum pump to port M.
7 START and race the engine and observe vacuum at port M. The vacuum should build at idle to an even reading, and no change in vacuum should occur regardless of engine speed. If no vacuum is formed, or vacuum readings are erratic, the M vacuum port is clogged. Clean the injection mixer port and retest. Remove the hand held vacuum pump, and reinstall the vacuum hose to port M.