- Raise the rear of the car until the wheels are clear of the ground by at least 4 inches. Support the car with safety stands.
- Disconnect the vacuum hose from the distributor vacuum advance chamber. This is the outer hose on cars with a dual diaphragm.
- Connect the hose to a vacuum gauge.
- Pour hot water on the temperature sensing switch to ensure that it is above 65°F. The temperature sensor is located on the right door pillar.
- Start the engine, apply the foot brake, and put the transmission selector lever in Drive.
- Slowly release the foot brake and allow the transmission to shift into high (third) gear.
- Have a friend observe the vacuum gauge while you raise the speed of the engine until the speedometer reads 35 mph.
- If the system is working properly, there should be no reading on the vacuum gauge until the speedometer reads 35 mph, at which time the vacuum gauge should show a reading.
- If the vacuum gauge shows a reading below 35 mph, a component in the electronic spark control system is defective. If the vacuum gauge does not show a reading, even above 35 mph, there is either a defective component in the electronic spark control system, or there is a broken or clogged vacuum passage between the carburetor and distributor.
See Figure 1
- With the engine completely cold, look inside the cold air duct and make sure that the valve plate is in the up position (the plate is closing off the cold air duct).
- Start the engine and bring it to operating temperature.
- Turn the engine OFF and look inside the cold air duct again. The valve plate should be down, allowing an opening from the cold air duct into the air cleaner.
- If the unit appears to be malfunctioning, remove it, examine it to make sure that the springs are not broken or disconnected, and replace the thermostat if all other parts appear intact and properly connected.
Transmission Valve (TRS)
- Attach a test light to the wire which connects the transmission valve to the distributor modulator valve.
- Jack up the vehicle so that the rear wheels are free to turn.
- Start the engine, and engage the transmission (manual or automatic) in a low gear. Observe the test light, which should be lighted at this time.
- On standard transmissions, engage high gear and check to see that the light goes out when high gear is engaged.
- On automatic transmissions, place the vehicle in Drive and allow it to fully upshift. Upon the shift into high gear, the test lamp should go out.
- If the test lamp fails to function properly, replace the transmission valve.