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Home >> Mercury >> 1983 >> Capri Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> THERMACTOR System >> Testing >> Extended Idle Air Bypass System
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Extended Idle Air Bypass System

  1. With engine at normal operating temperature and transmission in Neutral, insert a .140-.150" (3.5-3.8 mm) shim between the idle tracking switch (ITS) and the throttle stop. Begin timing.
  2. If after 2-1/2 minutes the thermactor bypass valve dumps secondary air through the vents, the system is okay. If not, check routing and condition of hoses. If hoses are okay, check bypass valve function.
  3. If valve is okay, check battery voltage to ITS and continuity through normally closed ITS while manually cycling switch. If okay, check that solenoid is functional and actually opens to close off vacuum. If solenoid is okay, turn engine off and ignition "ON" and check for battery voltage to MCU and to relay and for a signal to the solenoid.
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