How to Identify Piston Slap?

[Kayden]

Methods to identify piston slap are as follows: 1. At low speed, conduct a cylinder cut-off test for each cylinder. If the knocking sound reduces or disappears after cutting off, it indicates that cylinder is the source. 2. At idle speed, the piston slap is obvious and clear. As the engine temperature rises or the speed exceeds medium speed, the knocking sound weakens or disappears. 3. Remove the spark plug and inject a small amount of thick lubricating oil into the cylinder through the spark plug hole. After adding the lubricating oil, use the starter to rotate the crankshaft several times to fill the gap between the piston and cylinder wall with an oil film, then start the engine. If the knocking sound significantly weakens or disappears immediately after starting, but quickly reappears as the oil film is lost or burned, it confirms that cylinder is the source. 4. Use a long-handled screwdriver to touch the side of the engine block and listen for the sound. If the knocking sound is obvious and slightly vibrates, it confirms that cylinder is the source.