My 1997 Aerostar has a lack of power, and I hear a banging noise.

[mtclogo]

When I have the A/C turn on while driving sometime, seems like the car have no power to move on until I turn off the A/C then the car can move on?
Sometime i stop at the light, and start driving with 60km ir even go up the hwy with 100km, i heard the back of the van sound like somone kicking the backdoor, then the car low on power.

 

[BrooklynBay]

Are you hearing a banging sound from the rear differential? As for the lack of power, clean the MAF sensor, and replace the spark plug & cables.