I have a fluttering sound from the motor upon accelorating?

need more info. poss belt or tensioner noise?

Could be in the lifters need to get it inspected.

To reiterate what globalhelper said in answer #1....BELT or TENSIONER . Get someone in the vehicle to turn the A/C on and off while you watch the accessory drive belt. When the A/C is turned on , your increasing the load on that belt IF the TENSIONER OR BELT are worn past there usable life expectancy (yes , both would be considered normal wear items), you will see and most likely hear the noise you're describing.Watch and see if the tensioner is vibrating back and forth rapidly , matching the 'fluttering' sound you're hearing.IF the noise is a knocking or ticking then we're in a whole different ballpark. Good luck.