What Causes Engine Shaking and Why Does It Stop When Accelerating?

[LeRyan]

It may be due to changes in fuel injection volume, which inevitably causes the engine speed to fluctuate, resulting in shaking during idle. Below is some relevant information about engines: 1. Introduction: An engine is a machine capable of converting non-mechanical energy into mechanical energy. 2. Classification: Includes internal combustion engines, external combustion engines, jet engines, electric motors, etc. External combustion engines convert the thermal energy generated by combustion into kinetic energy; Watt's improved steam engine is a classic example of an external combustion engine. Internal combustion engines, or reciprocating piston engines, differ from external combustion engines primarily in that the fuel burns inside the engine. Jet engines are those that directly generate thrust by expelling high-speed gas streams through a nozzle.

[MacAniyah]

My car previously experienced severe engine shaking at idle that stabilized upon acceleration, mainly due to carbon buildup clogging the throttle body and intake passages. At low speeds, reduced airflow combined with carbon deposits causes incorrect air-fuel mixture ratios leading to unstable combustion and shaking. However, pressing the accelerator increases airflow, resulting in more complete combustion. Another possibility is aging spark plugs with insufficient ignition energy at low speeds causing cylinder misfires. Also, check the engine mounts - deteriorated rubber dampers amplify low-speed vibrations. Regular carbon cleaning is recommended, especially for city-driven vehicles frequently operating at low speeds; throttle body cleaning shows noticeable improvement. Additionally, excessively dirty air filters can affect idle air supply - these are all common causes.

[LaElias]

Idle shaking without shaking when accelerating is often caused by abnormal throttle opening. A dirty and stuck throttle can lead to insufficient air intake, causing unstable combustion at low idle speeds due to inadequate air supply. However, when the throttle is opened further during acceleration, the increased air intake eliminates the shaking. Additionally, carbon buildup on fuel injectors is another issue; at low speeds, the smaller fuel injection amount is more prone to clogging, leading to uneven fuel supply, whereas during acceleration, the larger fuel injection amount results in more uniform fuel delivery. If the spark plug gap is too large or the electrodes are eroded, weak ignition at idle can also cause shaking. In such cases, cleaning the throttle and fuel injectors can have a direct effect. Regularly adding fuel additives can reduce carbon buildup, and avoid cheap gas from small gas stations.

[Clarisse]

I've encountered this issue before. The mechanic at the repair shop diagnosed it as worn-out engine mounts. At idle, the failed damping of the engine mounts causes vibrations to transmit directly into the cabin, but when you step on the accelerator and the RPM rises, it moves out of the resonance range. Additionally, an overly lean air-fuel mixture can also cause this kind of shaking. An intake manifold leak or an EGR valve stuck in the open position can make the idle mixture too lean, but the mixture returns to normal when you accelerate. If the ignition coils are aging and their output is unstable, this can also happen, with noticeable misfires at idle but no issues during acceleration. It's best to run a computer diagnostic to check for trouble codes and read the data stream to pinpoint the problem.