Model: Polo 1.4L (manual) car
    Driving distance: 12000km
    Symptom: the owner reflects the morning when the car was started several times to start the car, after the start was particularly powerful jitter.
    Troubleshooting: into the workshop, starting two times before the car, start again, one can be a car. As the owner is reflected in the morning is not good start, so the fault should be judged in the cold when the more obvious. The car parked for a few hours, to be cold after the test again, three or four times to start, the body jitter particularly powerful, and then listen to the engine sound, according to experience to judge, the sound is the sound of the engine missing cylinder.
    There are four possible reasons for the lack of cylinder: ① spark plugs need to be replaced; ② ignition coil failure; ③ injector block; ④ cylinder pressure is too low. Connected to the 1552 computer diagnostic equipment for the engine to detect the data, the data are within the limits of the normal range. To determine the car computer aspects of the sensor data is normal, mechanical failure is more likely. After understanding, the car in nearly a year and a half only traveled 12000km, the basic for commuting, rarely run high speed. Analysis may be due to the valve caused by carbon deposition, but the specific reasons still need further testing to determine.
    First of all, may cause the engine to remove the cylinder one by one to detect. 1552 computer diagnostic instrument shows the ignition coil and injector working condition is normal. On the cylinder spark plug for fire test, spark plug work properly. Finally, the cylinder pressure test, there are two cylinder cylinder pressure below the standard value. New car caused by the cylinder pressure is mainly due to the inlet and exhaust valve seal is not strict, which further determine the bad start and valve carbon deposition. Observe the valve with the endoscope, found that the exhaust valve, especially in the intake valve on the coke is particularly large, thus determined that it is due to the coke to make the valve seal lax, burning is not sufficient. The car has been very serious coke, with no demolition cleaning can not be completely removed, so the need to remove cylinder head cleaning coke.
    Open the engine cylinder head found that coke has been quite serious, the coke cleared, re-assembly, start again (at this time for the cold state), one can start, the engine is not shaking, the phenomenon disappeared.