1. When the engine water temperature is low, the air conditioner is turned on, and the engine voltage is low, ECU programming should appropriately increase the idle speed. Under this normal condition, if the engine water temperature is normal, the air conditioner is not turned on, and the idle speed is high, it means that the system is faulty, which may be an electronic control system or a mechanical system.
2. If the idle speed is too high due to mechanical failure, be sure to check whether the intake pipe leaks, whether the vacuum pipe falls off and whether the intake pipe is damaged (the intake manifold of Volkswagen engine is mostly rubber pipe). Because the air intake of the engine is very small at idle speed, if there is air leakage, it will cause high idle speed.
3. Leakage of fuel injector may lead to excessive fuel supply, which may lead to higher idle speed than normal.
4. For EFI vehicles equipped with fuel vapor recovery system, fuel vapor should not enter the intake pipe at idle speed. If fuel vapor is sucked into the intake pipe at idle speed due to system failure, the idle speed is higher than normal.
5. After cleaning the throttle body and idle speed control valve, the engine may have a high idle speed after starting, which requires a learning process for the computer. Because the engine idle speed will decrease after the throttle body and idle speed control valve are dirty, in order to stabilize idle speed, ECU will control the opening of idle speed control valve or throttle valve to increase the intake air, thus stabilizing idle speed.
After cleaning, the ECU also controls the air intake according to the original opening, and the engine idle speed will increase.
If the idle speed of the car is too high, you can try the following methods:
Change the oil. When there is a problem with the idle speed of the vehicle, the first thing to look at is whether it is time to change the oil. Change the oil in time, otherwise the engine will be abnormal if it takes too long.
Pay attention to the choice of engine oil. Automobile oil should be of high grade, such as SJ grade or above. This kind of engine oil has better quality and good performance in all aspects.
Look at the antifreeze in the tank. The antifreeze in the water tank should also be checked more, neither less nor more, otherwise its effect will be affected and it will not play a good role in cooling the engine.
Pay attention to antifreeze. Generally, new cars need to be replaced every 2-3 years or every 40,000 kilometers. The antifreeze with suitable freezing point should be selected according to the regional temperature. For example, if the lowest ambient temperature is-10, the antifreeze of -25 should be selected.
Check the engine. If the idle speed of the vehicle is not the problem of engine oil and antifreeze, check the engine to see if there is any problem.
Check the oil circuit. Sometimes the idle speed of the vehicle is too high, and it is likely that there is something wrong with the oil circuit, such as a blocked throttle and so on.