Engine keeps revving at 2k randomly???

[LB197]

Ok so one night last week i was in mcdonalds drive through, and my car was revving at 750 revs then kept dropping (about every 3 seconds) to 500 revs and nearly cutting out, so i had a fiddle with the adjuster and thought id solved it, now when i turn it it starts revving at 2000 revs then starts dropping down or until i restart it but tonight it did the dropping to 500 again and nearly cut out, its getting a bit annoying now, is there a simple fix? Thanks in advance, luke

 

[S-Fell-89]

Clean the throttle body and idle valve

 

[LB197]

Ok ive cleaned those and it still does it, does anyone have any other suggestions, thanks.

 

[imprezaworks]

Idle air control valve maybe?

 

[da rok]

if uve adjusted something then im guessing it would have been that, a while back i had a issue where the engine would randomly rev to the limiter untill u switch it off and re start it, my coil packs were somehow causing that, bt at the moment when my cars warm it idles at 500 rpm and dosnt stall even when pulling off with out giving it some gas