Air Bypass Valve Info and testing

Ford air bypass valve

The ford ranger air bypass valve solenoid is used to control engine idle speed and is operated by the EEC-IV control module. This valve allows air to pass around the throttle plates to control:

1. cold engine fast idle
2. no touch start
3. dashpot
4. over temperature idle boost
5. engine idle load correction.

Symptoms of a bad one:

1. Engine stalling
2. Surging
3. Poor idle conditions
4. "Check engine light" on

Diagnosis:

The signal to the solenoid should be 1 volt or less at curb idle, (with all accessory loads off). Applying 12 volts to the solenoid will cause a neutral idle speed change greater than 1000 rpm. Check for shorts between both solenoid terminals and the case.

Codes 12, 13, 16, 17 & 19 all indicate idle speed is out of spec (too high or too low). Codes 47 and 48 indicate a fuel mixture problem which could be caused by an air leak. It may be possible to clean the ports with electrical safe clearer, do not use regular carb cleaner as it will remove the protective coating. Clean port holes in the manifold also before reinstalling.