Why is the crankcase ventilation pipe installed in front of the throttle?

Short for exhaust gas recirculation. Exhaust gas recirculation means that part of the exhaust gas discharged by the engine is sent back to the intake manifold and re-enters the cylinder together with fresh mixed gas. Because the exhaust gas contains a lot of polyatomic gases such as CO2, it can't be burned but absorbs a lot of heat because of its high specific heat, which reduces the maximum combustion temperature of the mixed gas in the cylinder, thus reducing the production of nitrogen oxides. I hope I can help you. There is something wrong with the car, find the car master. 4S shop professional technician, 10 minutes to solve.