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HOMESERVICE MANUALSMERCURY1983ZEPHYR GS, 2.3 A, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMTHERMACTOR SYSTEMTESTINGEXTENDED IDLE AIR BYPASS SYSTEM
1983 Mercury Zephyr GS, 2.3 A, Automatic

Extended Idle Air Bypass System

1983 Mercury Zephyr GS, 2.3 A, AutomaticSECTION 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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.