Spark plugs can clog and eventually foul if the engine is allowed to idle too low for too long. Throttling up an engine with oil-soaked spark plugs can help clear them out.
The engine should be at or above 800 RPM. Failure to do so may cause spark plug fouling. If the plugs do foul (the engine will sound rough), running the engine at a higher RPM will blow them clear within a few seconds by doing so.
Possible to simulate?