Idle HC/Co Concentration Check

NOTE: 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 2 minutes.
Insert HC/CO meter testing probe into intermediate pipe at least 40 cm (16 in).
Check HC/CO concentration at idle.

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