Hello. I have a 2001 Ford Taurus with a 3.0. Last couple of weeks it has been 'misfiring' in idle. When I start up the car, the engine shudders and shakes randomly like extra random heartbeats. When I am driving, there is no problem and the random shaking goes away but if I come to a stop light or sign, the engine will randomly shake again. Does not seem to affect the driveablilty of the car but is worrisome regardless. My check engine light has been chronically on for about a year but had a buddy run the code and it is due to a bad seal on my gas cap. I was wondering if it is due to a bad spark plug(s) or plug wire(s). Anyone with any insight?