Car problems are increasing, but these problems have been bothering us. For example, the unstable idle speed of hot cars has always been the biggest headache for car owners. So, do you know the reasons for the unstable idle speed of hot cars?
Causes of unstable idle speed of hot car
I. air intake system
① the first reason is the leakage of intake system, intake pipe and various valves. Air or enters from the intake pipe, gasoline vapor enters from the carbon canister valve, and exhaust gas enters into the intake pipe, which will cause the mixer to be too thick and too thin, resulting in abnormal combustion of the engine. ② Excessive fouling on throttle and intake ports. ③ Misalignment of idle air intake.
II. Mechanical structure
The first is the valve mechanism. The failure of the valve mechanism leads to excessive power reduction of individual cylinders, resulting in power imbalance. The second is that there is too much carbon on the valve working face and valve seat ring, resulting in loose valve sealing. The third is the engine body and piston connecting rod mechanism. Its failure will also make the compression pressure inconsistent.
III. blockage of exhaust system
And when the internal part of the three-way catalyst is blocked locally or randomly due to gelation, carbon deposition, crushing and other reasons, it will increase the back pressure during exhaust, make the vacuum degree of the intake pipe too low, cause incomplete exhaust and insufficient intake of the engine, and deteriorate the working performance of the cylinder. The engine shudders at idle speed. Poor air intake may also cause the computer to memorize the fault code of the air flow meter. If the fault is not eliminated for a long time, the oxygen sensor will work under harsh conditions for a long time, which will accelerate the damage of the oxygen sensor and cause the engine fault light to light up.
IV. fuel system
① fuel injector failure. If the fuel injector is dripping or blocked, it cannot inject fuel according to the instruction of ECU, resulting in too rich or too thin mixture, poor operation of individual cylinders and unstable idle speed of the engine. ② Fuel pressure failure. If the oil pressure is too low, the atomization state of the fuel ejected from the fuel injector is poor or the ejected fuel is linear. In serious cases, only oil droplets are ejected, and the fuel injection quantity is reduced, making the mixture too thin; If the oil pressure is too high, the actual injection quantity increases, making the mixture too rich. ③ The fuel injection quantity is inaccurate. Each sensor or circuit fault causes the control unit to issue wrong commands, so that the fuel injection quantity is incorrect, resulting in too rich or too thin mixture, which is an indirect cause of unstable idle speed.
V. ignition system
At present, almost all cars integrate the ignition module with the ignition coil, or use double ignition coils or direct ignition. First of all, if the fault of the ignition module will make the electric spark too weak or fail to ignite, for this measurement, it can only be said that for the model that can measure the stimulated voltage, the primary one can not be seen in the voltage, but the trigger signal of ignition can be measured. The reason for the ignition coil and ignition module may be the lack of ignition signal sent by the computer, or there may be a problem with the power supply line of the ignition module. This happens from time to time in the actual repair. The chance of a new car is quite high. When we repair a new car, some repairmen still look for it and find a lot of problems. For a new car, we still need to ensure its power supply, positive and negative, so that it can operate reliably.
What is a cold car and what is a hot car
(1) according to the engine coolant temperature, it can be divided into two states. If it is lower than 60 ℃, it belongs to cold vehicle, and if it is higher than 60 ℃, it belongs to hot vehicle.
(2) it can also be divided into two types according to the reaction degree of circuit module. The computer module and battery are placed for a long time and in a dormant state, which belongs to a cold vehicle; Automotive electrical modules and electrical components are in standby or running state, belonging to hot vehicles.