Engine idle problem fiesta st 2006

[Xr2/st/frazer]

Hi im new to the modern car as my daily is an xr2. Purchased 06 fiesta st150 with bottom end trouble so i bought a 30,000 mile engine from a 2008 st150 transferred all ancillaries to the new engine topped all fluids and started the car...idle shoots up to 4000rpm then drops to 3000rmp if u touch the throttle it goes up passed 4000rpm....any ideas on fault as i am totally lost as the old engine idled fine.
Many thanks frazer

 

[Sekred]

Try checking the throttle body. I have read on a few UK forums where periodical cleaning is required re ST150.

 

[Xr2/st/frazer]

Ive replaced the theottle body and its exactly the same

 

[Sekred]

Is it trowing codes?, there could be lots of reasons. Maybe its sucking air after the MAF sensor or throttle body.

 

[Xr2/st/frazer]

No codes came up apart from p2111 & p2110 but i think thats becouse we disconected the throttle body to see if it would tick over cleard them codes and they havent come up again. Going to plug into diagnostic tonight to see whats going on