You have can take your car to a parts store chain, most places do perform diagnostic tests for free. I would call them and check to see if they honor that statement. You can save money by going that route first. You may need to replace spark plugs, which can cause a possible misfire, and would be a sound explanation for your drivability concern.
My first thought would be that maybe you have a miss in one of your cylinders and it is not contributing to power the engine. The only way to know for sure is to bring the vehicle to your dealership and have them run some diagnostic checks. If it is a miss, it could be a bad spark plug or wire, or a stuck valve, or a bad fuel injector. Ask Patty has a list of female friendly and trustworthy technicians if you are looking for a good place to take your vehicle.
〉 Answered on Dec 28th, 2007 by Suzanne Grego, Technician at City of Philadelphia Fleet Management