Actually no, they don't if the mixture is very rich. No one's absolutely certain why it happens but they definitely miss a beat, fire, miss, fire and so on. If you go to the web page I do for my club you can see a graph (derived from cylinder pressures) of an engine in 4 stroking mode. It's a curious phenomenon and has a few surprises.

http://www.holdfastmac.com.au/instanttorque.html