What should you check if an engine shows hesitations when accelerating?

When an engine shows hesitations when accelerating, checking fuel quality is crucial. Poor fuel quality can lead to incomplete combustion, causing the engine to hesitate or misfire. Contaminants or water in the fuel can disrupt the fuel-air mixture necessary for proper engine performance. If the fuel has degraded due to sitting for too long or has been contaminated, it won't burn effectively, leading to hesitation during acceleration.

While other factors, such as oil levels, spark plug condition, and choke operation, might also impact engine performance, they are less directly related to acceleration hesitations than fuel quality. A deficiency in oil levels primarily leads to lubrication issues and potential engine damage rather than affecting acceleration, while spark plug problems can cause misfires or poor ignition but are secondary to fuel quality issues. Choke operation can affect engine performance during starting or cold conditions but is not typically related to hesitations during acceleration when the engine is warm. Hence, ensuring the fuel quality is the initial and most critical step in diagnosing such an issue.