Mitsubishi Montero (1991+). Manual - part 105

Fig. 10:  Typical Negative Backpressure EGR Valve

Courtesy of General Motors Corp.

         Digital EGR Valve

         The digital EGR valve operates independently of engine

manifold vacuum. This valve controls EGR flow through 3 orifices.

These 3 orifices are opened and closed by electric solenoids. The

solenoids are, in turn, controlled by the Electronic Control Module

(ECM). When a solenoid is energized, the armature with attached shaft

and swivel pintle is lifted, opening the orifice. See  Fig. 11.

         The ECM uses inputs from the Coolant Temperature Sensor

(CTS), Throttle Position Sensor (TPS) and Mass Airflow (MAF) sensors

to control the EGR orifices to make 7 different combinations for

precise EGR flow control. At idle, the EGR valve allows a very small

amount of exhaust gas to enter the intake manifold. This EGR valve

normally operates above idle speed during warm engine operation.

         Verify EGR valve is present and not modified or purposely

damaged. Ensure thermal vacuum switches, pressure transducers, speed

switches, etc., (if applicable) are not by-passed or modified. Ensure

vacuum hose(s) to EGR valve is not plugged. Ensure electrical

connector to EGR valve is not disconnected.

Fig. 11:  Typical Digital EGR Valve

Courtesy of General Motors Corp.

         Integrated Electronic EGR Valve

         This type functions similar to a ported EGR valve with a

remote vacuum regulator. The internal solenoid is normally open, which

causes the vacuum signal to be vented off to the atmosphere when EGR

is not controlled by the Electronic Control Module (ECM). The solenoid

valve opens and closes the vacuum signal, controlling the amount of

vacuum applied to the diaphragm. See Fig. 12.

         The electronic EGR valve contains a voltage regulator, which

converts ECM signal and regulates current to the solenoid. The ECM

controls EGR flow with a pulse width modulated signal based on

airflow, TPS and RPM. This system also contains a pintle position

sensor, which works similarly to a TPS sensor. As EGR flow is

increased, the sensor output increases.

         Verify EGR valve is present and not modified or purposely

damaged. Ensure thermal vacuum switches, pressure transducers, speed

switches, etc., (if applicable) are not by-passed or modified. Ensure

electrical connector to EGR valve is not disconnected.

Fig. 12:  Cutaway View Of Typical Integrated Electronic EGR Valve

Courtesy of General Motors Corp.

         SPARK CONTROLS (SPK)

         Spark control systems are designed to ensure the air/fuel

mixture is ignited at the best possible moment to provide optimum

efficiency and power and cleaner emissions.

         Ensure vacuum hoses to the distributor, carburetor, spark

delay valves, thermal vacuum switches, etc., are in place and routed

properly. On Computerized Engine Controls (CEC), check for presence of

required sensors (O2, MAP, CTS, TPS, etc.). Ensure they have not been

tampered with or modified.

         Check for visible modification or replacement of the feedback

carburetor, fuel injection unit or injector(s) with a non-feedback

carburetor or fuel injection system. Check for modified emission-

related components unacceptable for use on pollution-controlled

vehicles.

         AIR INJECTION SYSTEM (AIS)

         Air Pump Injection System (AP)

         The air pump is a belt-driven vane type pump, mounted to

engine in combination with other accessories. The air pump itself

consists of the pump housing, an inner air cavity, a rotor and a vane

assembly. As the vanes turn in the housing, filtered air is drawn in

through the intake port and pushed out through the exhaust port. See

Fig. 13.

         Check for missing or disconnected belt, check valve(s),

diverter valve(s), air distribution manifolds, etc. Check air

injection system for proper hose routing.

Fig. 13:  Typical Air Pump Injection System

Courtesy of General Motors Corp.

         Pulsed Secondary Air Injection (PAIR) System

         PAIR eliminates the need for an air pump and most of the

associated hardware. Most systems consists of air delivery pipe(s),

pulse valve(s) and check valve(s). The check valve prevents exhaust

gases from entering the air injection system. See  Fig. 14.

         Ensure required check valve(s), diverter valve(s), air

distribution manifolds, etc., are present. Check air injection system

for proper hose routing.