2002 Rover 25 high revs

Maybe or engine coolant temp sensor

ive replaced the cts

Try cleaning IAC and passageways. check for vacuum leaks also clean throttle body maybe carbon on plate

ive try cleaning the iacv but a sealed unit,cleaned the tb and ive tried spraying wd40 on engine for leaks i think i can hear a leak but not sure if this is normal

For vacuum leak use carb cleaner when it hits leak idlewill change.

where do i spray the carb cleaner to find leak,if there is no air leak is the iacv at fault

Try unpluging IAC and repluging can you hear motor run? I don't have acess to Rover info but there should be test proceedures like Ohm checks.

when i turn the engine off i can hear the motor on the iacv working but how far should the plunger move,when i tried cleaning and switched the igniton on i saw the plunger move

Could try an experiment remove IAC and plug off airway. Start see if it still idles at 1500

ive tried removing the iacv and plugging up the airway but the car will not start unless someone is manually opening the butterfly vakve on throttle body i have changed the cts but is it possible that they supplied me with the wrong one

That tells me that air is not getting around throttle plate so IAC looks suspect.

ive replaced the iacv with a secondhand one and still the same problem but i cant hear any air leaks now is it possible the lambda sensor is faulty

https://www.2carpros.com/forum/2002-rover-25-high-revs-vt337616.html
Check out this post almost same problem. Maybe you two should exchange notes