What is required to perform a proper compression test EXCEPT?

To achieve accurate results during a compression test, specific procedures are essential. Holding the throttle blades wide open allows for maximum airflow into the cylinder, ensuring that the engine can pull in as much air as possible, which results in a more representative compression reading. A fully charged battery is vital because it supports the starter motor in cranking the engine at an appropriate speed, thereby achieving an accurate compression test. Additionally, testing with the engine at operating temperature ensures that all components, including piston rings and cylinder walls, are properly expanded and functioning as they would during normal operation.

In this context, while it is standard practice to remove the spark plug for the cylinder being tested to facilitate the compression reading, it is not necessary to remove only that spark plug. In fact, it is common practice to remove spark plugs from all cylinders. This approach reduces resistance on the starter motor, allowing it to crank the engine more freely and obtain a more accurate compression measurement across all cylinders. Thus, the removal of only the specific spark plug for the test is not a requirement for performing a proper compression test.