What Causes Engine Shaking at Idle When Warm?
2 Answers
Reasons for engine shaking at idle when warm: 1. Damaged idle control valve, unable to regulate the opening of the air passage, resulting in uncontrolled air intake; 2. Clogged fuel injectors, or fuel pump malfunction, or obstructed fuel lines, leading to uncontrolled fuel injection; 3. Throttle body malfunction with air leaks, causing uncontrolled air intake; 4. Faulty air intake sensor, resulting in uncontrolled air intake; 5. Engine control logic error, unable to maintain stable idle speed. Common causes of engine shaking include excessive throttle body dirt or fuel injector carbon buildup. When there's too much carbon deposit inside the engine, gasoline sprayed by the cold-start injector gets largely absorbed by the carbon deposits, making the air-fuel mixture too lean during cold starts and causing difficulty in starting. The solution is to clean the fuel system and check the idle control valve for carbon deposits, which should be cleaned if present.
There are quite a few reasons for engine shaking at idle when warmed up. I've experienced it before—after the engine warmed up, the car felt wobbly, which was really annoying. Usually, it's related to ignition system issues, such as dirty or worn-out spark plugs that need timely replacement; otherwise, unstable ignition can cause shaking. Another possibility is a fuel system malfunction, like clogged fuel injectors due to carbon buildup, leading to uneven fuel delivery. Or, it could be due to broken engine mounts, causing the engine to be improperly secured. Additionally, faulty sensors, such as the oxygen sensor, can also lead to unstable idle speeds by affecting the air-fuel mixture ratio. Although these issues may seem minor, neglecting them long-term can damage the engine and increase repair costs. So, I recommend getting it checked at a professional shop as soon as you notice the problem. Replacing spark plugs or cleaning fuel injectors only costs a few hundred bucks, saving you a lot of hassle. Don’t forget, regular maintenance can prevent such issues—don’t wait until the shaking gets worse to take action.
