Idle HC/Co Concentration Check

IMPORTANT:  This check is used only to assist with idle HC/CO Diagnostics.

• Initial Conditions:
  • Engine must reach normal operating temperature.
  • Air cleaner installed.
  • All pipes and hoses of air induction system connected.
  • All vacuum lines properly connected.
  • All fuel system wiring connections fully plugged.
  • Transmission in P (Park) or N (Neutral) range.
  • Tachometer and HC/CO meter calibrated and in hand.
• Run engine at 2500 rpm for approximately two minutes.
• Insert HC/CO meter testing probe into intermediate pipe at least 40 cm (16 in.).
• Check HC/CO concentration at idle.

IMPORTANT:  Wait at least 1 minute before measuring to allow concentration to stabilize. Complete measuring within 3 minutes. If HC/CO concentration does not conform, see the following HC/CO diagnostic chart for possible causes.