Pulse Air Feeder (PAF) System

Fig. 31 Pulse air feeder (PAF) system. 4-156/2.6L engine:

This system, Fig. 31, is used on 4-156/2.6L (2.6 liter) engines. It supplies secondary air into the exhaust system between the front and rear catalytic converters in order to promote the oxidation of exhaust emissions in the rear catalytic converter.
The PAF consists of a main reed valve and sub-reed valve.
The main reed valve is actuated in response to movement of a diaphragm which is activated by pressure pulsation generated by the reciprocating motion of the number 3 piston. The number 3 cylinder crankcase is sealed by a seal cover which has a small hole for discharging engine oil and blow by gases.
The sub-reed valve is actuated by exhaust vacuum generated from pulsation in the exhaust system between the front and rear catalytic converters.