Variable Induction System: Testing and Inspection

Resonance Control Schematic:

RPM / THROTTLE CONDITION
The resonance flap, located in the plenum, closes via the changeover valve creating a short pipe effect and substantially increasing power when:

^ Engine speed is less than 4,120 rpm and the throttle is wide open
^ Engine speed is greater than 6,720 rpm and throttle is wide open

If the above conditions are not met the flap remains open maintaining a long pipe condition. This "long pipe" condition is better suited for low- and mid-range load conditions.

To prevent repeated open and closing of the flap during constant engine speeds of either 4,120 of 6,720 rpm, a delay of the switchpoint depending on whether approaching form lower or higher engine rpm is incorporated.

Resonance Actuator Location:

RESONANCE CONTROL ACTIVATION
- The plate must open and close twice briefly after every start (self-test). Verify by observing the motion of the actuator linkage.

If not, check for damaged or defective actuator, vacuum lines, changeover valve, or Resonance Flap Control Unit.

Changeover Valve Location:

CHANGEOVER VALVE
- With the ignition ON, check voltage at terminal 1 of the changeover valve electrical connector (X6131).

Voltage = 12 volts. If not, check the green wire to the ignition switch for short or open.

- Check for ground at terminal 2 of the changeover valve electrical connector (X6131).

Ground must be provide twice briefly after every start.

Replace the changeover valve if vacuum is not provided to the actuator under the above conditions.

Resonance Control Unit Location:

CONTROL UNIT TEST
- The control unit must provide ground to the changeover valve twice after every start.

If not, refer to SCHEMATIC DIAGRAMS for circuit checks. If OK, replace the Resonance Control Unit.