Surging 99 v10 f250 4x4
 

Running down the road at around 1500 rpms and about 35-45 mph when i let off to coast down like a hill or even flat road the truck starts surging from 1000-1200 rpm up to 1400-1700 rpms until i get back on the gas. Any ideas what is going on?

Any surging at idle ?? My first thought would be vacuum leak somewhere..

It dont do it constantly just started after i had the airbag fuse blow i replaced with proper amp fuse and now it surges when i let off the accelerator some times. Wouldnt vacuum be constantly surging?

And it use to surge after a long trip once i put it in park and sat idling it would surge sometimes it surge from 750-800rps to 1000rpms and fall back to 750 instantly

Idle Air Control valve? MAF sensor? Vacuum Leak? Throttle position sensor?

What i was thinking was throttle position sensor would it throw a code only code the is thrown atm is my emissions cause i had to take catilytic converter off