Engine Emission Control

Engine Emission Control - 6.2L (2V), 6.8L (3V)

System Overview

NOTE: Do not permanently remove or render inoperative any part of the Vehicle Emission Control System including related hardware. Failure to comply may violate applicable state and federal law.

NOTE: The vehicle emission vacuum routing diagrams are contained in the Description and Operation subsection of the Evaporative Emission system. For additional information, refer to Evaporative Emissions Evaporative Emissions.

The Positive Crankcase Ventilation (PCV) valve, is a one-way valve that uses intake manifold vacuum to ventilate blow-by gases from the crankcase and returns the gases to the intake manifold for combustion.

Component List

The gasoline engine emission control system consists of the:

- PCV valve on the 6.2L (2V) is located on the RH valve cover.
- PCV valve on the 6.8L (3V) is part of the LH valve cover.
- PCV tube is connected from the PCV valve to the PCV fitting.
- PCV fitting is bolted to the intake manifold.

System Components

The PCV valve varies the amount of blow-by gases returned to the intake manifold based on available engine vacuum.

The PCV tube carries the blow-by gases from the crankcase to the PCV fitting.

The PCV fitting connects the PCV tube to the intake manifold and is heated on the 6.8L (3V).

System Operation

As an engine runs, high-pressure gases are contained within the combustion chamber. Piston rings seal against the cylinder preventing the high pressure gases from passing into the crankcase between the side of the piston and the cylinder bore. Some amount of gas always leaks past the piston rings into the crankcase. If this blow-by gas could not escape then pressure would build up within the crankcase. Should the intake manifold's pressure be greater than the crankcase the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again.

It is critical that the parts of the PCV system be kept clean and open, otherwise air flow will be insufficient. A plugged or malfunctioning PCV system eventually damages an engine. An engine's poorly maintained PCV system eventually becomes contaminated with sludge, causing serious engine problems.