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Operation
EGR (Exhaust Gas Re-circulation) Valve General Guidelines
The EGR valve is an example of a valve that is actuated by vacuum. With no vacuum applied, the
EGR valve is closed and no exhaust gas is re-circulated. As a vacuum is applied the valve opens
and exhaust gas can re-circulate.
MAP (Manifold Absolute Pressure) Sensor General Instructions
Attach the 30cm length of plastic tubing onto the vacuum pump's braked fitting. Attach the
other end to the vacuum port on the map sensor. Pump the vacuum pump until the gauge
needle registers approximately 15"Hg of vacuum. The gauge needle should stay at that pressure
and should not drop. If it does not hold its vacuum, replace the map sensor.
In operation, the map sensor sends a return signal to the vehicle's electronic control module. In
some cars, this signal varies in frequency between 160Hz and 85Hz, depending on vacuum level.
To check the electrical characteristics, a frequency metre is necessary in addition to the vacuum
pump. Manufacturer's specifications should be reviewed prior to testing.
Computerised Engine Control Devices
•
Barometric Pressure (BARO) Sensor
•
Positive Crankcase Ventilation (PCV) System
•
Exhaust Gas Re-circulation (EGR) System
•
Manifold Air Pressure (MAP) Sensor
Ignition Control Devices
•
Vacuum advance distributor
•
Retard Control Valve （RCV）
•
Spark Delay Valve （SDV）
Systems Testing
•
Air condition and heating controls
•
Cruise control systems
•
Headlight cover doors
•
Fuel tank and line testing
•
Vacuum door lock systems
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