The engine control unit constantly monitors the following elements that play an important role in emissions management:
- efficiency of the catalytic converter;
- correct installation and integrity of the dust filter in the cabin (if it is installed);
- continuity of circuits and serviceability of all actuating elements of fuel injection and adjustment of the ignition timing (fuel injection);
- any component or system, the failure of which can lead to the excess of the threshold value of permissible toxic emissions (EGR system, preheating system, automatic transmission).
On engines 1.9 l (WJZ) the process is controlled by the electronic recirculation unit according to the signals of the contact sensor of the extreme position of the fuel pump regulator lever, the engine temperature sensor and the crankshaft speed sensor. The recirculation valve is mounted forward on the intake manifold and is connected to the exhaust manifold with a metal pipe. The valve has a vacuum chamber with a diaphragm and a solenoid operated valve. When the solenoid valve is open, the vacuum from the vacuum pump of the brake system enters the vacuum chamber. The diaphragm opens the valve through the rod, and the exhaust gases begin to flow into the cylinders.
On engines 1.9 l (WJY) recirculation is controlled by the fuel injection control unit. The recirculation valve is the same as on the WJZ engine and works similarly.
On the 2.0 liter engine, the process is controlled by the fuel injection control unit. The system consists of a recirculation valve and a control valve. The recirculation valve is installed on the exhaust manifold, and the control valve is on the intake manifold. Both valves have vacuum chambers with diaphragms, which are supplied with vacuum from the vacuum brake booster pump through the control solenoid valves.