The mileage is about 80 thousand km. The model is C307, carrying the 1.8L engine and the 4 speed automatic transmission in 2012 Changan Ford Fawkes car. User response: the engine of the vehicle is jitter, sometimes even flameout. Inspection and analysis: the maintenance personnel first determine the authenticity of the fault, in the cold car and the hot car through a number of simulation tests, found that when the failure occurs, the engine has a lack of cylinder phenomenon. There are many reasons for this failure, such as ignition, intake and so on. The connection fault detector IDS detected. The fault code showed that the 1 cylinder was short of fire and the fuel injection volume was too small. Enter the data recorder, check the fuel correction amount, found no abnormalities. Check each cylinder ignition and power balance, normal. Check the freeze frame data and find that the coolant temperature is - 40 C. Therefore, according to the analysis of the circuit diagram, this phenomenon should be caused by the poor contact between the coolant temperature sensor and the engine control unit. During the inspection, the hand just touched the connector C589 of the engine control unit, and the data flow immediately showed that the coolant temperature was - 40 C, and the engine was abnormally jitter at this time. This shows that the problem is here, so we have checked the needle No. 30 of C589, and there are signs of loosening. Troubleshooting: dealing with the connector, troubleshooting.