What Causes the Idle Vibration When the Air Conditioning is Turned On in a Fit?
2 Answers
The reasons for idle vibration when the air conditioning is turned on in a Fit are as follows: 1. Engine control logic error, unable to receive the air conditioning activation signal: When it cannot determine whether the air conditioning is turned on, the engine control unit (ECU) mistakenly considers it as a temporary high load and attempts to compensate for the resistance at idle by increasing the engine speed. When the engine speed drops, it cannot handle the load from the air conditioning compressor and increases the speed again, leading to repeated adjustments that manifest as unstable idle. 2. Air conditioning control circuit error, unable to send the air conditioning activation signal: Since the ECU cannot determine the air conditioning status, it continuously adjusts the idle speed, resulting in unstable idle. 3. Air conditioning circuit malfunction, causing intermittent operation of the air conditioning: When the air conditioning is not working, the air conditioning compressor belt runs without load, so it does not affect the engine load. The intermittent operation of the air conditioning compressor causes the engine to continuously adjust the idle speed, leading to unstable idle.
I've been driving a Fit for several years and have also encountered the issue of idle shaking when the air conditioning is on. This is mainly because when the AC is turned on, the compressor starts, requiring the engine to exert extra effort. The Fit's small displacement engine tends to become unstable under heavy load. If the engine mounts are aged or worn out, their shock absorption effect diminishes, making the shaking more noticeable. Sometimes, if the idle speed control valve is dirty, it can affect the stability of the RPM, leading to similar issues. The checking method is simple: start the car without turning on the AC and observe the idle, then turn on the AC and compare the shaking intensity. If the difference is significant, prioritize checking the engine mounts and the compressor connection components. Regular maintenance, such as cleaning the throttle body and inspecting the mounts, can reduce the likelihood of this problem occurring. It's quite annoying when the car starts shaking, and safety always comes first.
