Suzuki Liana's idle speed is still unstable, jumping between 800 and 900, and there is no fault code. What is the reason?

There are many reasons for idling vibration of EFI vehicle, such as air leakage at air inlet, poor atomization of fuel injector, poor ignition performance of spark plug, low cylinder pressure, carbon deposition on valve, dirty idle motor of throttle valve, stuck solenoid valve of carbon canister, damaged egr solenoid valve, damaged oxygen sensor, and engine cylinder missing. Let's look at it with a decoder. Check the air inlet for air leakage. Check the cylinder pressure. Replace the aging spark plug. Check whether the carbon canister solenoid valve and egr solenoid valve are stuck in the normally open position. Remove the throttle for thorough cleaning, and match and replace the throttle assembly if necessary. Check and replace the damaged oxygen sensor.