What are the reasons for engine shaking at idle?

[LeMadeline]

Engine shaking at idle is mainly caused by: 1. Unstable oil pressure. If the fuel pump's supply pressure is abnormal or the intake pressure sensor values are incorrect or malfunctioning, it can cause body shaking. Solution: Check oil pressure and replace components if necessary. 2. Severe engine carbon buildup. When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold start injector can be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts, making it difficult to start and causing the car to shake. Solution: Clean the fuel system and check if the idle control valve has carbon buildup that needs cleaning. 3. Ignition system issues. Poor performance of the ignition system or bad spark plug firing can also cause car shaking. Solution: Check if the spark plugs have excessive carbon buildup and replace them if necessary.

[LeEloise]

I've been driving for many years and often encounter car shaking at idle. I've summarized several common causes. The most common is ignition system issues, such as aging or worn spark plugs that fail to ignite properly, causing unstable engine operation and resulting in body vibration. Another cause is the fuel system; clogged fuel injectors or poor fuel line flow leading to insufficient fuel supply can also cause shaking. If the engine mounts are worn or cracked, their shock absorption deteriorates, making the car shake as if dancing. Carbon buildup is another persistent issue; carbon deposits on intake valves or pistons affect the air-fuel mixture ratio, making the car prone to shaking at idle. Once, my car shook severely, and after inspection, replacing the spark plugs and cleaning the fuel injectors solved the problem. I recommend regular maintenance, such as checking spark plugs every 20,000 kilometers, which can prevent many issues and even save some fuel costs.

[OGavin]

As a DIY car enthusiast, I've found that idle shaking mostly stems from system imbalances. Ignition issues top the list - when spark plugs or high-voltage wires fail, misfires occur, making the engine shake like an earthquake. The fuel system can't be ignored either; clogged injectors or dirty fuel filters disrupt fuel supply, leading to unstable idling. Intake leaks or dirty air filters cause abnormal airflow, resulting in excessively lean or rich mixtures and significant engine speed fluctuations. Engine mounts are the most easily overlooked - when rubber pads deform or break, vibration damping fails, causing noticeable body resonance. At home, I use an OBD scanner to read trouble codes and eliminate these simple issues first. If shaking persists, I then consider ECU control or sensor faults. Regular carbon deposit cleaning is crucial too; using fuel additives can extend engine life.

[Norman]

My old car often idles with vibrations, so here's some personal insight. When spark plugs age, their filaments may break or the gaps widen, causing misfires and engine imbalance. Carbon buildup in fuel injectors leads to uneven fuel spray and incomplete combustion, making the car shake when idling. Worn engine mounts are also common—deteriorated rubber reduces vibration absorption, transmitting shakes to the body at idle. Air system issues like intake leaks disrupt the air-fuel ratio, making steady idle RPM hard to maintain. Carbon deposits in the throttle body or cylinder head reduce space and hinder smooth operation. Ignoring these issues increases fuel consumption and accelerates part wear. Replacing damaged components early and keeping things clean will make the car run much smoother.