Idle Hydrocarbon and Carbon Monoxide Concentration Check. Saturn SL 1997

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 1997 🢒 SL 🢒 Engine 🢒 Engine Controls - 1.9L 🢒 Idle Hydrocarbon and Carbon Monoxide Concentration Check

Important: This check is used only to assist with idle HC/CO diagnostics.

Check for the following 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).

Important: 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.

Check HC/CO concentration at idle.

General Diagnostic Information HC/CO Diagnostic Chart

Symptoms

Causes

High

Low

Rough Idle, Very Lean Air-Fuel Ratio Causing Misfire

Faulty Ignition:

•	Incorrect Timing

•	Broken/Faulty

•	Secondary Wire/Coil

•	Fouled, Shorted or Improperly Gapped Plugs

Vacuum Leak

•

PCV Hose

•	Intake Manifold/Gasket

•	Throttle Body/Gasket

•	Brake Booster/Hose

•	Engine Pre-conditioning

High

Normal

Rough Idle, Low Power/High Oil Consumption

•	Leaky Intake and/or Exhaust Valves

•	Faulty Lifters

•	Leaky EGR Valves

•	Leaky Head Gasket or Cracked Head

•	Worn Valve Guide Seals

•	Worn Rings/Valve Guides

•	Faulty Catalytic Converter

•	Engine Pre-conditioning

High

Low

Rough Idle (Black Smoke From Exhaust), Extremely Rich Air-Fuel Ratio

Faulty Fuel System and/or Faulty Electronic Fuel (System)

•	Faulty Pressure Regulator-High Pressure Fuel

•	Clogged Fuel Return Line

•	Damaged Intake Air Temperature Sensor

•	Faulty PCM

•	Faulty Fuel Injector

•	Faulty Throttle Position Sensor

•	MAP (Manifold Absolute Pressure) Sensor

•	Restricted PCV Valve

•	Damaged Oxygen Sensor

Normal

High

Poor Fuel Economy, Poor Idle, Low Power

Faulty Fuel System

•	Idle Speed

•	Fuel Injector Leaking

•	PCV System Clogged

•	Plugged Air Filter

•	Faulty Pressure Regulator-High Fuel Pressure

•	Faulty Catalytic Converter

•	Engine Pre-conditioning