Positive Crankcase Ventilation (PCV) and Exhaust Gas Recirculation (EGR) Service
PCV System Hoses and Grommets Deteriorate From Lack of Maintenance and Aging
The PCV system requires a free flow of air through the engine to work properly. The PCV valve and breather element should be regularly replaced to ensure complete scavenging of the crankcase gases.
Lack of regular tune ups and oil changes produces rapid sludge build up in the engine. PCV hoses and grommets soften and collapse or clog up. The result is little or no air flow in the PCV system. Now the loosely fitting grommets and hoses cause vacuum leaks. The engine may idle poorly, stall, and set trouble codes.
A worn engine with excessive blow-by will overwhelm the PCV system.
A higher than normal idle air control value on a scan tool may indicate a restricted PCV system or a dirty throttle body.
A High Idle Control Value (IAC) May Indicate a Clogged PCV System
Clogged EGR Passages Caused By Lack of Maintenance
EGR - General Service Issues:
Restricted EGR Passages
Clogged EGR passages are common across many manufacturers. The intake manifold or throttle body assembly may have to be removed to properly access and clean the passages.
Some systems measure the change in engine vacuum by monitoring the MAP sensor signal as the EGR valve is cycled open and closed. This confirms EGR operation. If the EGR passages are clogged, this can lead to misdiagnosing EGR system components such as the EGR valve, solenoid, or sensor, instead of the real underlying cause.
Some manufacturers, such as Toyota and Nissan, use an EGR temperature sensor to monitor EGR flow. If EGR passages are restricted or the tip of the sensor is covered in carbon deposits, the sensor response will be weak and the PCM may set an EGR related trouble code.