System Test

Fig. 26 Throttle Positioner Adjusting Screw:

1. Remove air cleaner.
2. Start engine and attain normal operating temperature.
3. Disconnect the vacuum hose from the upper-most TP diaphragm and plug the hose.
4. Disconnect the vacuum hose from the EGR valve and plug the hose.
5. Set the first step TP setting speed by turning the TP adjusting screw, Fig. 26. Make adjustment with electric cooling fan OFF.


1st Step Setting Speed: 1100 rpm

Fig. 27 Throttle Positioner Diaphragm:

6. Reconnect the vacuum hose to upper-most diaphragm.
7. Disconnect the vacuum hose from the lower-most TP diaphragm and plug the hose. Fig. 27
8. Check that TP is set at second step speed.

2nd Step Setting Speed: 1800 - 2200 rpm

9. Reconnect the vacuum hose to the lower-most TP diaphragm.
10. Check that the engine returns to idle speed within 2 - 6 seconds.
11. If a problem is found, inspect each component of the TP system.
12. Reconnect the vacuum hose to the EGR valve.
13. Stop engine and reinstall air cleaner.