Idle Hydrocarbon and Carbon Monoxide Concentration Check. Saturn L100/L200/LW200 2002

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2002 🢒 L100/L200/LW200 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Idle Hydrocarbon and Carbon Monoxide Concentration Check

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

•	Initial conditions:

-	The engine must reach normal operating temperature.

-	The air cleaner is installed.

-	All pipes and hoses of the air induction system are connected.

-	All vacuum lines are properly connected.

-	All fuel system wiring connections are fully plugged.

-	The transmission is in P (Park) or N (Neutral).

-	The HC/CO meter is calibrated and in hand.

•	Run the engine at 2500 RPM for approximately 2 minutes.

•	Insert the HC/CO meter testing probe into the 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 HC/CO concentration does not conform, see the following HC/CO diagnostic chart for possible causes.

•	Check the HC/CO concentration at idle.

HC/CO Diagnostic Chart

Symptoms

Causes

High

Low

Rough idle, very lean air-fuel ratio causing misfire

Faulty ignition:

•	Incorrect timing

•	Broken/faulty ignition components

•	Secondary wire/coil

•	Fouled, shorted, or improperly gapped plugs

Vacuum leak:

•	PCV system

•	Intake manifold/gasket

•	Throttle body/gasket

•	Brake booster/hose

High

Normal

Rough idle, low power/high oil consumption

•	Leaky intake and/or exhaust valves

•	Faulty lifters

•	Leaky EGR plate gasket

•	Leaky head gasket or cracked head

•	Worn valve guide seals

•	Worn rings/valve guides

•	Faulty catalytic converter

High

Low

Rough idle (black smoke from exhaust), extremely rich air-fuel ratio

Faulty fuel system

Faulty electronic fuel (system):

•	Faulty pressure regulator-high fuel pressure

•	Clogged fuel return line

•	Damaged intake air temperature sensor

•	Faulty PCM

•	Faulty fuel injector

•	Faulty throttle position sensor

•	Manifold absolute pressure (MAP) sensor

•	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