Discovery Series I

Check base idle speed using a Land Rover TestBook. Ensure Idle Air Control (IAC) valve is set to 20-25 steps at idle. Ensure Mass Airflow (MAF) sensor output voltage is approximately 1.4 volts at idle. If necessary to adjust idle speed, locate by-pass screw in plenum chamber. Using a self-tapping screw, remove tamper-proof plug covering by-pass screw. Use TestBook to monitor idle speed while turning by-pass screw. Ensure there are no loads, the transmission is in Park or Neutral and air suspension (if equipped) is in standard position and disabled. Install NEW tamper-proof plug over by-pass screw after rechecking idle speed.