timing belt or air leak?
 

I have a 00 concorde & getting code 0456, EVAP system air leak. Have inspected all hoses & seals w/o finding a problem. Was sitting at stop light today & car idled high for a second then idle dropped as if the car was gonna shut down. Have noticed that if I slow down or speed up, the car will jerk slightly & idle high for a few seconds. Will an air leak cause this to happen, or should I try replacing the timing belt? Had a 93 mazda 929 last year with similar problems & timing belt broke. Is there any way to have the timing checked on car to see if timing is off? Mileage is 130k, bought the car 4 months ago, & I don't know if belt has been replaced or not. Thanx

RE: timing belt or air leak?
 

that code has nothing to do with a timing belt. Have you checked the plenum gaskets or plenum itself for that matter for the idle issue?

the trouble code is most likely a hose or seal. you need to make sure the gas cap gasket is good, and don't forget the fuel tank hoses and pump seal.