GM Metro/Sprint 1985-1993 Repair Guide

Idle Up System

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OPERATION



The ECM sends an electric signal to the Three Way Solenoid Valve (TWSV). Receiving the signal, the TWSV opens its inner valve and transmits the manifold vacuum to the idle-up diaphragm. As the diaphragm moves down by the vacuum, the idle-up adjusting screw and adjusting rod also move down and push the throttle lever to open the throttle valve a little for the idle-up state.

On manual transmission equipped vehicles, this system operates at idle and compensates for engine loads as a result of electrical loads for lights, cooling fan, rear defogger or heater fan.

On automatic transmission equipped vehicles, this system operates when the selector lever is shifted into D , 2 , L or R range and vehicle speed is below 15 mph. The system also operates when the temperature of the oxygen sensor is low and the sensor is not satisfactorily activated.

ADJUSTMENT



The idle-up actuator operates even when cooling fan is running. Therefore, idle-up adjustment must be performed when cooling fan is not running.

Manual Transaxle
  1. Warm engine to normal operating temperature.
  2.  
  3. While running engine at idle speed, check to ensure that idle up adjusting screw moves down when lights are turned ON .
  4.  
  5. With lights turned ON check engine rpm. Be sure that heater fan, rear defogger, engine cooling fan and air conditioner are OFF .
  6.  
  7. Engine rpm should be at specified idle speed or 50 rpm higher. If not, adjust using idle up adjusting screw located at top of idle up solenoid.
  8.  
  9. Check idle up system as described above with the heater fan, rear defogger, engine cooling fan and air conditioner are all operated separately.
  10.  

Automatic Transaxle
  1. Warm engine to normal operating temperature.
  2.  
  3. While running engine at idle speed, check to ensure that idle up adjusting screw moves down when brake pedal is depressed and shift selector lever is moved to D range. All accessories should be OFF .
  4.  
  5. Check engine rpm. Engine rpm should be at specified idle speed or 50 rpm higher. If not, adjust using idle up adjusting screw located at top of idle up solenoid.
  6.  

 
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