Sub Systems

Procedure
1. Disconnect vacuum hose from EGR valve and install a "tee" fitting and connect a vacuum gauge with a long hose into the vacuum line.

2. Raise front and rear wheels off ground.

WARNING: Vehicle must be safely and securely supported. Very high engine and tire speed required to perform the following test.


3. With vacuum gauge visible, start engine and allow to run at fast idle for about 3 to 4 minutes. At curb idle speed the vacuum gauge should read zero.

4. Place transmission in third gear for manual transmission and in drive for automatic transmission. Observe the speedometer and vacuum gauge. Increase engine speed. The vacuum reading should increase. At about 67 mph the vacuum reading should drop to zero, indicating that the EGR High-Speed Modulator subsystem is functioning properly.

5. If system is not functioning properly check the vacuum solenoid valve. Disconnect the electrical leads from the valve to isolate it from the electronic amplifier.


CAUTION: Never connect any test jumper or test light to the valve unless it is isolated from the amplifier, as severe damage to the amplifier will result.


6. Connect jumper wires from the valve terminals to the battery and to a ground, operate engine in neutral at about 1500 rpm. The valve should close when power is applied. If there is a vacuum reading replace the valve.

7. If there is no vacuum reading with the valve energized, check for power at the amplifier connector using a self powered test light. If there is no power, check and repair the ignition switch circuit. If there is power check ground connection. If grounded properly, check speed sensor for continuity with an ohmmeter laced across sensor. The resistance should be 40 to 60 ohms. If the speed sensor is functioning properly, replace the amplifier.