Volkswagen Workshop Service and Repair Manuals

The exhaust gas is removed from the exhaust gas manifold -1- and entered into the intake manifold -3- via the vacuum controlled exhaust gas recirculating valve -2-. Actuation is by vacuum from the vacuum pump -4- whilst control is by the automatic glow period control unit (J179) -8- via the exhaust gas recirculation two-way valve (N161) -5-. When engine is cold, or at full load, or certain revolutions and at altitudes above 1000 m the exhaust gas recirculation is switched off as follows:

• ◆ At temperature below +50 °C (engine cold) the exhaust gas recirculation is switched off via engine temperature sender (G27) -6-.

• ◆ The partial throttle switch (F166) -7- for exhaust gas recirculation, on the injection pump ensures that the exhaust gases are only recirculated during part throttle operations.
• ◆ Engine speed cut-off is effected by the automatic glow period control unit (J179) -8- and alternator terminal W -9-. Thereby when the speed exceeds 1200 rpm, the exhaust gas recirculation is interrupted for 2 seconds and in excess of 3200 rpm, switch off.
• ◆ At altitudes over approx. 1000 m the exhaust gas recirculation is switched off by the altitude correction switch in automatic glow period control unit -8-.