ASE Gasoline Engines (T1) Practice Test 2025 – The All-in-One Guide to Master Your Certification!

Engine misfires, rough idle, and poor acceleration are indicative of a faulty ignition system because these issues directly relate to the combustion process's effectiveness in an engine. The ignition system is responsible for creating the spark necessary to ignite the air-fuel mixture in the engine cylinders. When the ignition system is not functioning properly—due to faulty spark plugs, ignition coils, or other components—it can lead to incomplete combustion. This results in misfires, where the engine might skip firing in one or more cylinders, causing it to run unevenly (rough idle) and decreasing power output (poor acceleration). These symptoms are clear indicators that the ignition system requires attention to ensure optimal engine performance and efficiency.

In contrast, better fuel economy, increased horsepower, and improved engine starting are signs of a properly functioning ignition system, as they reflect enhanced engine performance and efficiency rather than issues.