Cause analysis of solving high idle speed fault of hot car

(i) Excessive idling of hot car. When the engine is cooled, it can run at a fast idle speed under normal circumstances, but the idle speed is too high because it remains at a fast idle speed after the hot car is started. ) 2) The fault reason of high hot idle speed is 1. Throttle blocked or unable to close. 2. Improper idle speed adjustment. 3. The additional air valve is faulty. 4. The idle speed control valve is blocked or the control circuit is faulty. 5. The coolant temperature sensor is faulty. 6. The air conditioning switch and power steering pressure switch are faulty. 7. Crankcase forced ventilation device failure. 8. Air leakage in the air intake system. 9. The generator charging voltage is too low. (III) Fault diagnosis and elimination of excessive idle speed of hot cars; excessive idle speed is caused by excessive intake air or incorrect engine control signal. When the high idle speed is caused by air temperature sensor, cooling water temperature sensor, throttle position sensor, air flow meter/intake pressure sensor, switch signal, idle speed control valve, throttle body, fuel injector and vacuum to eliminate abnormal engine idle speed, please perform the following steps. 1. Check whether the throttle valve is fully closed and whether the throttle cable is stuck when idling. Shake the waist by hand and move the throttle valve in the closing direction. If the engine idle speed can be reduced to normal speed, the throttle valve is not locked. If the throttle cable is blocked, replace the cable. When the throttle shaft is blocked, please remove the throttle body for cleaning. 2. Re-adjust the idle speed and reset the engine computer according to the specified steps of this engine. Resetting the engine computer means erasing the fault memory of the engine computer and letting it learn idle speed again. When the engine reaches normal temperature and the idle valve is completely closed, most electronically controlled engines set the basic idle speed to (500 (plus or minus 50) rpm. When the adjustment and setting are invalid, further inspection is needed. 3. Check the air inlet system pipe joint and vacuum hose for air leakage. 4. Perform fault self-diagnosis. If there is a fault code, find the cause of the fault through the displayed fault code. If conditions permit, you can further read the dynamic data stream, mainly observing the load signal of the engine, the opening or control steps of the idle speed control valve, the pressure signal of the engine intake system, the temperature signal of the coolant and various switching signals. 5. Check the coolant temperature sensor. After unplugging the harness plug of the water temperature sensor, when the idle speed of the engine returns to normal, it means that the water temperature sensor is faulty, and a low coolant signal is input to the computer. It is worth noting that after unplugging the plug of the water temperature sensor, the engine fault indicator lights up, the computer fault safety function starts, and the water temperature is automatically set to 80 degrees. After unplugging the harness plug of the coolant temperature sensor again, the fault code of the coolant temperature sensor still exists on the professional computer. In contrast, you can connect the computer and delete the fault code, or you can disconnect the computer fuse of the engine for about 30 seconds after the engine stops, thus deleting the fault code of the computer. 6. Clamp the crankcase forced ventilation pipe covered with soft cloth with pliers. When the engine speed decreases, the crankcase forced ventilation valve leaks air at idle speed, and the engine intake air is too large, which will affect idle speed. Please replace the crankcase forced ventilation valve. 7. Check the additional air valve. Clamp the additional valve air inlet hose wrapped with soft cloth with pliers. If the engine idle speed can be reduced to normal speed, it means that the additional air valve cannot be closed after warm-up, so it is necessary to check whether the power cord of the additional air valve is normal. If it is normal, please replace the additional air valve. 8. Check the idle speed control valve. After the engine is turned off, unplug the harness of the idle speed control valve and plug it in after starting. If the engine changes, the idle speed control valve works normally. Otherwise, please check the control line or replace the idle control valve. 9. When the air conditioner switch is turned on or the steering wheel is turned, if the engine speed cannot be further increased, it means that the automatic idle control system is out of order, and the air conditioner switch, power steering pressure switch and automatic idle control pipeline are 10. If the battery voltage is too low for a long time, the rapid speed of the engine will also become higher. Please measure the charging voltage of the generator. When it is lower than 12V, check the charging system.