The term "miss" in car talk is that one... or a few... spark plugs are not firing in the cylinder at the correct intervals.
I would check the spark plugs.
There are a number of factors that we could get into for the cause of a "miss", a lot has to do with mileage.
If a spark plug is fouled by bad gas or mileage the only thing to do is replace them.
Engines have cylinders - 4, 6 or 8 are the most common engines. Each cylinder has a valve to let air in, a valve to let air out, an injector to let gasoline in, a spark plug, and a piston at the bottom of it. When the air and gas is let in, the piston moves up to compress the mixture, the spark is ignited and there is a controlled explosion in the cylinder, forcing the piston down. When your engine is "missing", either one or more of your cylinders is not performing this controlled explosion. This may cause a "bumpy ride" feeling and will definitely reduce power in the vehicle. Reasons for an engine to miss include no spark from the spark plug, no gas to the cylinder, a stuck valve that is not allowing air into the cylinder etc. A great place to actually see an engine work is on howstuffworks.com. I hope this helps!
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〉 Answered on Aug 27th, 2007 by Suzanne Grego, Technician at City of Philadelphia Fleet Management