eng surges up at start up 1994 S/420
 

when i start my car up the eng, seem,s to rev,, up for about 5,,to 10,, sec and then it calm down it seem,s like it,s some kind of vacum pressure or somethig can any one help me to I.D. the part that my be makeing the car do this every time i start the car some time,s it,stall out and i have to try to re,,start it,, like it seem like it not geting enoug air or some thing,,, ihave never had the cap,,, and rotor,, change could this be the cause,,,THANK,S MEL DWYER 94/S420