Why is the abnormal noise of BMW 740i engine shaking the exhaust pipe?

The most common cause of automobile jitter is that the throttle valve is too dirty or the injector has too much carbon deposit; Abnormal noise of exhaust pipe caused by three-way catalytic blockage.

When there is too much carbon deposit in the engine, the gasoline sprayed by the fuel injection head will be absorbed by the carbon deposit during the cold start, which leads to the lean mixture during the cold start and makes it difficult to start.

In this case, only when the gasoline absorbed by carbon deposits is saturated can it easily enter the car. After getting on the bus, the gasoline adsorbed on the carbon deposit will be sucked into the cylinder by the vacuum suction of the engine for combustion, and the mixture will become thick, and the combustible mixture of the engine will be diluted and concentrated, resulting in idling jitter after cold start.

The lower the temperature, the more oil is needed for cold start, and the existence of carbon deposit will affect the smooth start.

Solution: clean the oil circuit, check whether there is carbon deposit in the idle motor, and clean it.

The function of three-way catalytic converter is to reduce noise while purifying exhaust gas. For different cars, the three-way catalytic converter is different, and the length, thickness and density of the filter element inside are also different, depending on the fluidity of the exhaust gas.

Regular cleaning of the three-way catalytic converter can eliminate the abnormal sound of the exhaust pipe. Million car purchase subsidy