[Car question and answer] When the car is idling while stopped, it vibrates finely. What is the cause and is there a solution?

First, check to see if the engine is running in a "good" state

There are several possible causes for idling vibrations. However, before that, it is important to check from the basic maintenance side of the engine. I would like to think about whether it is properly maintained and whether regular replacement parts and periodic inspections specified by the manufacturer are being performed. If the car is over 10 years old, it may be time for regular replacement of various parts, so let's take a look at some.

First of all, have you forgotten to replace the intake system of the engine and the air element? Taking a gasoline engine as an example, the three basic conditions of "good air-fuel mixture/good compression/good ignition" must be met in order to operate normally.

If the air element is not replaced for a long time and it is not possible to inhale well, the rotation tends to become unstable. Even if there are no symptoms during driving, the rotation during idling is not constant, and it may be transmitted as vibration. If you step on the brake and stop the car while in the D range, the old torque converter AT does not perform neutral control, so it is possible that the load will be applied and the rotation will be uneven.

Checking and replacing the air element is relatively easy, so even users can do it. If the vehicle is regularly inspected at the dealer, the air element should be replaced regularly.

If you have checked the air element and it is clean, the next suspect is the ignition (spark) plug. Even cars from 10 years ago often use platinum plugs or iridium plugs that use platinum in the spark-producing electrodes. The feature of this plug is the long replacement cycle. The replacement time recommended by the manufacturer is often set at 100,000 km, and if the car is 10 years old, it may be past the replacement time. There are many times when the guideline for replacement (mileage and time) is written on the back of the hood or near the engine, so if it has passed, I would like to replace it without hesitation.

Actually, in the past, I also made a mistake related to plug replacement timing. When his car's odometer reached 100,000 km, he knew it was time to replace the platinum plugs. However, considering the margin of the manufacturer's recommended replacement time, I forgot to replace it while I was thinking "After running a little more". There were no troubles or malfunctions, and the fuel economy was good.

After that, when the mileage exceeded 160,000 km, I noticed that a light knocking sound called "chiri chiri" was occurring while driving. As a trial, premium (high-octane) gasoline with high anti-knock performance was put in, and unexpectedly, when the outside temperature dropped, the symptoms disappeared even with regular gasoline. However, soon after that, the tinkling sound developed into an idling disorder accompanied by a coughing vibration, a clearly abnormal condition. So I finally thought about the cause and remembered that I had to replace the spark plugs. It is natural because it was over 60,000 km from the recommended replacement time.

The next thing I want to check is the dirt on the intake electronically controlled throttle. Vehicles that did not replace the air element, in particular, may experience poor idling due to dirt inside the intake throttle. Although such dirt can be removed with a commercially available cleaner, it is better to have it inspected and cleaned at a dealer or repair shop. Vehicle diagnostic equipment may be able to determine if the throttle is malfunctioning.

Considering that the car is over 10 years old, you should doubt the engine mount. In particular, "liquid-filled engine mounts" become more susceptible to vibration as they deteriorate. Even if it is made of general rubber, it may crack due to deterioration over time, and in some cases it may be cut. This is the same for the transmission mount, so I want to check it at the same time. In order to inspect it in detail, it is necessary to lift it up, so it may be better to leave this to a dealer or a maintenance shop.

So far, we have introduced several possibilities, but it is difficult to identify the cause of vibration, and there are cases where it is caused by an unexpected failure of a part unrelated to the engine. An experienced mechanic is more likely to find the cause quickly, so we recommend having a professional inspect it. (Text: Makoto Maruyama)

Vibration at idle 5