Fault phenomenon
    A Santana passenger car, the cumulative travel of 350,000 km. The car in the driving, when the shift lever from 1 block into the 2 block or 2 block into the 3 block when the car has a clear "hair red" phenomenon, and when the other gear is basically normal.
    Failure check analysis
    According to the experience of maintenance, the cumulative stroke of more than 350,000 km of the car, there is driving "hair" failure, often the intake air temperature - intake pressure sensor is caused by coke blockage. Inspection also found that the engine intake manifold also exist more coke. The root cause of the formation of coke is the engine cylinder and piston clearance is too large, the oil fleeing into the combustion chamber combustion, combustion part of the exhaust gas in the exhaust gas recirculation process into the intake manifold, plus the valve due to wear or carbon deposition is not closed Yan, the passage of time in the intake manifold to form coke, and the intake air temperature - intake pressure sensor blockage. As a result, the intake pressure signal delivered by the sensor to the ECU does not correspond to the actual intake air amount, resulting in a reduction in the fuel injection amount. The engine is too lean to burn due to the mixture, so that the oil is supplied during the low gear shift Poor, there is a clear "hair red" phenomenon.
    Clear the intake manifold and intake air temperature - the inlet pressure sensor coke, while replacing the piston ring, grinding valve installed after the test drive, the fault disappears.