the car belongs to a trader came in for mot and failed on emissions he went away and changed the air filter,plugs,oil&filter and cleaned the throttle body out,he came back to see if it would pass but it did,nt the revs were now stuck on 1500-2000 rpm i put it on the kts for him and tried to reset it but to no avail he went away and fitted a new cat and oxy sensor ,this got the car through but it failed on the idle test he then renewed the throttle body(second hand) this was same as his old one,he left it with me to look at,i checked for air leaks,checked all vac pipes and checked he had done nothing wrong. every thing checks out ok but it will not reset the idle the fault codes are all relevant to high idle the voltage to the unit is spot on and the ohms readings are near enough i cant see the second hand unit having the same fault as the first but i cant see what he has done wrong ,any one else had similar problems i clean this type of throttle body regular and never have any problems any ideas