What Causes a Car to Shake When Starting but Run Smoothly Afterwards?
1 Answers
If your car shakes at idle but runs smoothly when driving, it is recommended to check whether the throttle body, fuel injectors, and idle air control valve need cleaning. This is because when accelerating with the throttle, the issue of insufficient fuel supply at idle is masked. Common causes and solutions for vehicle idle shaking: 1. Spark plug issues: If the spark plugs in the car's ignition system malfunction, it can lead to poor ignition system performance, weak spark plug firing, and other problems, resulting in unstable idle conditions. Solution: Inspect the condition of the spark plugs, high-voltage wires, and ignition coils. Check for excessive carbon buildup on the spark plugs and clean or replace them immediately if found. 2. Fuel quality issues: Poor fuel quality can damage engine performance, leading to idle shaking. Solution: Clean the throttle body promptly, which can usually resolve common issues. If the problem persists, professional repair is necessary. 3. Excessive carbon buildup or engine aging: Excessive carbon deposits inside the engine can absorb a large amount of fuel sprayed by the injectors during cold starts, resulting in a lean air-fuel mixture and difficulty starting. Once the carbon deposits become saturated with fuel, the engine starts more easily. However, the fuel adsorbed on the carbon deposits is then drawn into the cylinders by the engine's vacuum, enriching the mixture and causing idle shaking after a cold start. Solution: Clean the fuel system and check the idle control valve for carbon buildup, cleaning it if necessary.
