Old Focus Revs Problems

[winchy]

hi ive an ford focus mk1 v reg 1999 i believe and is a 2.0 ztec.

its just started to revs low when stopped at lights etc and seems like its going to stall (it don't stall though) there seems a tiny lack of power. I've cleaned the throttle valve checked all the basic like oil and water there all fine.

it just happened while i was driving

air from the back is very poppy, like its breathing in and out fast

(sorry i dont know the proper word for stuff)

any help would be great

thanks

[Barry_]

Sounds like it maybe a idle speed control valve issue. Either that or maybe the timing is out??