The travel mileage is about 140 thousand km, with the 4G20D42.0L double top cam 16 valve electronically controlled gasoline engine (the engine using Delphi electronic control system), and the 5 speed manual transmission of the 2009 SY6513HSIB cup sea lion. Fault phenomenon: the car owner states that the car in the near period of dry morning cold car does not step on the accelerator pedal, and the engine will be extinguished immediately after the engine starts to start, and sometimes even starts the three or four times the engine can't stand fire (that is, the cold car has no idle speed), but if the accelerator pedal starts to start the engine, the engine will stabilize the accelerator pedal after the engine is running. If the engine runs for 3~5 min, it will not extinguish, that is, the normal idle state. In addition, the engine fault lamp has always been bright, and there are no other abnormal phenomena during driving. Fault diagnosis: according to the description of the owner and the principle of the idling control of the electronically controlled engine, the author preliminarily analyzes the possible factors that cause the non idle speed of the cold car of the electronically controlled gasoline engine: the throttle valve body bypass port dirty plug, the throttle position sensor and its line fault, the idling control valve ISC (or the step motor) fault, the air filter Too dirty, serious combustor carbon, bad fuel quality, engine ECU failure. (Note: it will make the cold car start with no instantaneous high idle speed, especially in winter, especially in winter, and because of the high ambient temperature in summer, the cold car engine starts the moment is normal idle speed, about 750r/ min, so idling generally won't flameout.) . In addition, in the case of normal engine power, the possible factors that cause engine fault lights are: camshaft position sensor and its line fault (Note: in Delphi electronic control system, many types of camshaft position sensor 3P connector is not connected, after the engine starts the car, idle idle speed, acceleration smooth), The malfunction of the solenoid valve and its line in the activated carbon tank (more seen in the Delphi electronic control system), the failure of the post oxygen sensor and the bad contact of the engine related sensor lines. Since the car owner in the morning to the factory earlier, after the car, the engine is close to the state of cold car, more convenient to verify the failure phenomenon, through the repeated verification of the failure phenomenon, as the car owners. In order to promote the scientific diagnosis, use the brain to repair the car, repair the car quickly and repair the car in good faith, the vehicle engine was tested with the X-431 diagnostic instrument. Read the fault code: "PO140 after oxygen sensors open (E class)", clearing the fault code can be cleared, but after the engine reboot, engine fault lights will be lighted again, reading fault code is still. Data flow reading engine idle speed, data flow: engine relative load 5.5%, coolant temperature 66-C, short-term fuel correction (group 1) 0%, long-term fuel correction (group 1) 8.6%, intake manifold absolute pressure 32kPa, engine speed 798r/min, speed (0km/h, 1 cylinder ignition timing 8Deg; inlet temperature) 56 V, the throttle position sensor sampling 0%, the throttle position 0%, the front oxygen sensor voltage 0.79V (data change), the pre oxygen sensor short-term fuel correction - 0.78%, the post oxygen sensor voltage 1.10V (no change), the fault indicator (MIL) odometer 3845km, ignition voltage 13V; target idle 787r/min, The atmospheric pressure 102.50kPa, air fuel ratio 14:1, engine running time 385s, calculated air flow 2.00g/s, the front oxygen sensor reaction dilute to thick jump times 0 Counts, the front oxygen sensor is thick / thin to thin / concentrated reaction rate 0.00:1. The data flow is basically normal through the observation of the soil data flow, and only the post oxygen sensor data stream has no voltage change. The possible factors behind the failure of the post oxygen sensor are the failure of the post oxygen sensor itself and the breakdown of the signal line of the post oxygen sensor. After dismantling the post oxygen sensor, the heating coil is measured in an infinitely large state (that is, unconnected). A new oxygen sensor is replaced by a new oxygen sensor. After the engine starts the car, the fault lamp is no longer bright. After repeated verification, the data flow of the post oxygen sensor is also restored to normal: the intake temperature is 37, the voltage of the front oxygen sensor is 0.83V, and the post oxygen is after the oxygen sensor. Sensor voltage 0.78V, fault indicator lamp (MIL) odometer (0kra, ignition voltage 14V). For the car engine cold car without idle speed failure, considering the high mileage of the car, and the special characteristics of the engine throttle installation force one position (Note: the maintenance personnel are seldom willing to remove the throttle valve body for thorough cleaning during the maintenance of the vehicle, because the position of the valve body is located in the accessory driver's seat. " Under the chair, the disassembly is more troublesome; therefore, the maintenance personnel generally use the related brand cleaning agent to clean the inlet of the intake port. It is doubtful that the bypass port of the throttle valve may be too dirty to cause the cold car without idle speed. In order to verify the authenticity of the fault judgment, the seat, the floor below the seat, the floor, and the entrance are removed. Gas pipe, throttle valve body assembly, remove the throttle valve body to find that the throttle is really dirty, especially the throttle valve body bypass and stepping motor working cone, as shown. Troubleshooting: after the car's throttle valve body is thoroughly cleaned and loaded, the engine is running smoothly at idle speed, the acceleration is more relaxed and fluent, and the engine cold car has no idle fault completely disappeared. Fault summary: through this case also can be seen, now the auto repair industry, in the maintenance of vehicles, for the benefit of the maximum, customers enter the factory for vehicle repair, the front desk service consultant (receptionist) will repeatedly sell maintenance, protection and other products to the owner, the intake, fuel system cleaning, protection... ... Often the customer money is spent, the final problem is not solved, such as the intake system cleaning, although the maintenance personnel used related cleaning agent to clean the engine intake system, but the standard is not cured, the car is an example, 20 days ago, the customer was here to eliminate "the so-called air intake, fuel system cleaning." "Package", but the reason why the cold car does not idling is caused by the dirty inside the throttle valve. Is the throttle valve body not an intake system? It is believed that this is related to the incentive mechanism of a maintenance enterprise, and it is related to the professionalism and morality of the maintenance personnel. In particular, some young maintenance personnel, in the work, look at the "money", as long as there are no items on the work list, even in the process of maintenance and maintenance, the customer vehicles are found to have other differences. Common phenomena, such as: headlights are not bright, brake lights are not bright, or belts are abnormal, rain scrubbers do not spray water, tire pressure is low...... But he just didn't care about it. He was afraid he'd done more. If a customer like this doesn't keep up in good time, will it not lose? Here, I hope that the owners and maintenance personnel of automobile repair enterprises will stand by their customers' standpoints. Only if you are good, I am good and everyone is good, is it really good! With the rapid development of automotive electronics technology, automobile technology is changing day by day. Many middle and high grade cars have adopted electronic throttle. After cleaning the throttle valve body, professional instruments must be matched. Therefore, the maintenance personnel should be careful when maintaining and maintaining the vehicles, and can not be throttle to all vehicles. Door cleaning is a generalization, otherwise it will cause engine failure to start normally or abnormal engine idling.