Do you know there are many reasons for high idle speed?
Causes of high idle speed of automobile
1. The idle switch is not closed
Diagnostic method: turn on the air conditioner and turn the steering wheel at idle speed. If the idle speed of the engine does not increase, it proves that the idle switch is not closed.
Troubleshooting adjust or replace the throttle position sensor.
2. The idle speed control valve is faulty
Diagnostic method: check the action sound of the idle control valve. If there is no action sound, the idle control valve is faulty.
Troubleshooting: clean or replace the idle speed control valve, and use the special decoder to set the idle speed basically.
3. Air leakage of intake pipe
Diagnostic method: if you hear the "Chi Chi" sound of leakage in the intake pipe, it indicates that the intake system is leaking.
Troubleshooting: find the leakage, re seal or replace relevant components.
4. Valve timing error
The diagnosis method is to check the cylinder pressure, ⊿ PX and timing mark. If the cylinder pressure or ⊿ PX is not within the standard value range and the timing mark is incorrect, it can be judged that the valve distribution phase error has occurred.
Troubleshooting: check the timing mark and readjust the valve timing according to the standard.
5. The fuel injector leaks or is blocked
Diagnostic method: use a stethoscope to check whether the fuel injector makes a "creak creak" sound or measure the fuel injection quantity of the fuel injector. If the fuel injector has no action sound or the fuel injection quantity exceeds the standard, the fuel injector is faulty.
Troubleshooting: clean and check the fuel injection quantity of each fuel injector and confirm that there is no blockage and leakage.
6. The exhaust system is blocked
The diagnosis method is to use a vacuum gauge to detect. If ⊿ PX is low and there is often a dull sound during acceleration, it can be determined that the three-way catalytic converter is blocked.
Troubleshooting replace the three-way catalytic converter.
7. EGR valve is opened under idle condition
Diagnostic method: remove EGR valve. Block the exhaust gas recirculation channel and the fault disappears.
Troubleshooting this fault is mostly caused by the carbon deposit on the EGR valve stuck in the normally open position. The fault can be eliminated by eliminating the carbon deposit on the EGR valve or replacing the EGR valve.
What are the causes of unstable idle speed after cold start
In general, this may be due to a large amount of carbon deposition in the oil circuit system. If there is too much carbon deposition, the air intake will be too low and the mixture will be too thin, which will eventually lead to shaking after the vehicle is started.
Note: under the condition of low temperature in winter, the vehicle carbon deposit is too heavy, the vehicle ignition is difficult to reach the ignition point, and it is relatively difficult to start; In the case of high temperature in summer, carbon deposition has little impact on vehicle starting. Vehicle ignition is easy to reach the ignition point, and it is easier to start.