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Hagerty Employee

Piston Slap: Yes, another question about piston slap

Calvin writes:

I have a Acura 1.8L engine that overheated and now has piston slap. Is this bad, or can I just drive it until it is time to replace the engine? The car runs fine except for the slapping sound ...


Sajeev answers:

As we’ve discussed in the past, piston slap is usually more of an annoyance rather than an issue compromising engine performance or durability. But I am a little concerned it happened after an overheating incident. Does that sound go away at engine speeds above idle ..?


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New Driver

Thank you for the reply. I have been driving the Acura for 2,500 miles with no problems. oddly though, the car runs best (idle, acceleration) when the map sensor is disconnected.  Any thoughts?

Community Manager

Odds are the sensor needs to be cleaned ( or replaced.  They are pretty cheap, about $50 on Rockauto, so I'd recommend doing something.  Unplugging the MAP only hurts performance and economy. 


If it's wrist pin noise, it could be because a piston got hot enough to warp the piston, and the wrist pin is tight in it's bore. This can cause a piston slap noise, but the root cause of the noise is the tight pin. I've seen this when pistons get hot, and also from detonation. I also would just run it, unless there was concern that damaging the block would be an issue. The eventual failure mode could be a broken piston and the rod, flailing around, could damage the cylinder bore. 

Community Manager

That makes a LOT of sense, thank you for sharing!