Reasons for Unstable Engine Idle and Vibration

[VonAyla]

Engine vibration and unstable idle can be caused by various factors, which can generally be categorized into three systems: the intake system, ignition system, and fuel system. Any component failure in these systems may lead to engine vibration and unstable idle. The detailed reasons for unstable engine idle and vibration are as follows: 1. Common faults in the intake system: excessively rich or lean air-fuel mixture, excessive impurities in the throttle body and intake manifold, and inaccurate air intake measurement. 2. Common faults in the ignition system: spark plug issues, high-voltage wire problems, and failures in the ignition module or ignition coil. 3. Common faults in the fuel system: injector malfunctions, impurities in the fuel injector, and fuel pump problems.

[Lyla]

I've been driving for almost twenty years, and there are quite a few common reasons for unstable idle and shaking. The most common one is carbon buildup in the engine, especially on the intake valves, which affects the smoothness of the air-fuel mixture combustion. Old spark plugs can also cause this, as their ignition capability deteriorates, leading to uneven flames at idle. Clogged or dirty fuel injectors result in poor fuel atomization, causing uneven combustion in the cylinders and resulting in shaking. Additionally, a dirty air filter can restrict airflow, making the engine 'starve' and shake. It's best to regularly check the spark plugs and clean carbon deposits to prevent small issues from turning into big troubles. Don’t ignore idle shaking—it can make driving unstable and pose safety risks. I recommend getting a professional diagnosis; sometimes a simple cleaning can fix the issue.

[OJaxon]

In my first year of owning a car, I encountered an idle shaking issue where the car would shake like dancing at red lights. It turned out to be caused by a vacuum tube leak, allowing too much air to enter and creating an improper mixture, leading to unbalanced combustion. A clogged fuel injector can also cause similar issues, resulting in uneven fuel spray. Additionally, if the idle control valve gets stuck and becomes inflexible, the idle speed can fluctuate unpredictably. The mechanic emphasized the importance of fuel injector cleaning, and replacing the fuel injector significantly improved the situation. Older cars are more prone to such problems, especially during cold starts. Compression issues, such as uneven cylinder pressure, can also cause shaking. It's advisable to use a diagnostic tool to check pressure values to avoid missing any repairs. Addressing these issues promptly can prevent further engine damage from worsening vibrations.

[SanJaxon]

When modifying cars, idle vibration issues are often encountered, mostly due to ignition system failures. Weak sparks from aging high-voltage wires or coils, improper spark plug gaps, can all lead to unstable combustion. Additionally, worn-out engine mount rubbers losing their cushioning effect transmit vibrations to the body, exacerbating the shaking. Excessive carbon buildup in fuel injectors causing inaccurate fuel spray, leading to a strong fire with insufficient fuel contrast. Compression ratio imbalance, such as piston ring wear causing air leakage, also affects idle stability. After modifying ignition components, it's essential to test idle performance to avoid counterproductive effects. Cleaning and replacing key components are crucial experiences.