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.

[MadisonDella]

I've experienced engine knocking issues before, which feels like the engine makes a metallic ticking or pinging sound during acceleration, especially more noticeable when climbing hills or suddenly stepping on the gas. I confirmed it through repeated testing: start the car, drive at low speed with no problem, then suddenly accelerate—if you hear a sound like a small hammer tapping, it might be engine knocking. Once it happened on a business trip, and I initially thought it was a tire issue. Later, after inspection, it turned out to be poor fuel quality and improper ignition system settings. I quickly switched gas stations and dealt with carbon buildup, which fixed the problem. Now, before every drive, I pay attention to changes in sound, as ignoring it could lead to engine overheating or severe wear, affecting its lifespan. I recommend always listening for unusual noises.

[DominicFitz]

As someone who frequently deals with vehicle issues, I recommend starting with a simple auditory test to diagnose engine knocking: drive the car normally and pay special attention to whether there are any metallic knocking sounds from the engine area during rapid acceleration at medium to high speeds. These sounds are typically described as 'clattering' or 'popping' and are usually located near the cylinder area. If you suspect engine knocking, find a safe stretch of road to simulate the condition by revving the engine in neutral, observing whether the sound intensifies with increasing RPM. Additionally, check for common causes such as worn spark plugs or using fuel with an octane rating that's too low, as these often contribute to the problem. Regular maintenance is key to preventing such issues. Safety first—if you detect any problems, don't ignore them; get them checked immediately.

[McMarley]

Identifying engine knocking isn't actually difficult, it mainly relies on listening and feeling: When you accelerate while driving, if the engine produces continuous short metallic knocking sounds, like small drum beats, it's very likely. My car had this issue before, initially thought it was a belt problem, but upon closer listening, the sound was concentrated under the front hood. If it disappears or lessens after acceleration, you should be alert. Regularly using high-quality fuel and preventing spark plug carbon buildup are key to prevention. Early detection can save on repair costs.

[DiRachel]

I remember when I was learning to drive and heard knocking for the first time, I really thought it was a big problem. The sound was a sudden rattling noise during acceleration, somewhat like machine parts fighting each other. Later, after consulting experts, I learned to self-check: start the engine and drive steadily at low speed, then suddenly floor the accelerator to listen for any harsh metallic knocking sounds during the instant of acceleration. The key is to test multiple times in a safe place to confirm. If present, it might be due to incorrect fuel octane rating or improper ECU settings. Beginners shouldn't panic—just take it to a professional shop promptly to avoid cylinder damage.