【Fault description】
    A driving about 100,000 km BMW (BWM) 735 sedan, the engine starts increasingly difficult, and accompanied by power down, accelerate the difficulties, idling instability and so on.
    【Inspection process】
    In the maintenance of the engine, the cylinder spark plug found more serious, put on a new spark plug, the situation slightly improved, but soon there are coke, the phenomenon is still fault. In the inspection of the engine fuel system of the nozzle, also found that more serious coke, has hindered the injector fuel injection. We have carried out cleaning, inspection and commissioning of the injector, although the fault has been alleviated, but still exists. From the spark plug, injector coke serious phenomenon, it is not difficult to speculate that the engine combustion chamber until the exhaust pipe, silencer, coke is certainly very serious. On the engine to do speed test, found that the speed can be raised directly from the start to 2500r / min, but then accelerated, but not up. Running nearly 1 hour after the speed down to 2000r / min below, and there is a clear engine nausea, poor exhaust feeling. So unload the exhaust system and then try to start the engine as if all of a sudden sober, speed very smooth, the maximum speed can be raised to 4000r / min, and the idle speed can be stabilized at 700r / min or so, indicating that the fault is caused by exhaust system blockage of.
    【Fault Analysis】
    According to the information provided by the owner, the car is caused by the use of leaded gasoline. Leaded gasoline will destroy the best air-fuel ratio, the same combustion will produce more lead and lead, plug in the catalyst carrier pores, resulting in exhaust blocked.