Mk3 clio 1.5 dci . when i turn off ignition, the engine stll runs,

when i turn on engine , all is ok , but when i turn off the ignition and remove the key , the engine continues to run ,, if i start the engine , without touching the accelerator, it can be switched off , but if i press on the accelerator then try to turn off the engine , it does not stop,,,,,,,it takes a number of attempts with the key to eventually stop the engine , ive tried a new ignition barrel , changed the ecu , along with uch ,upc,and steering lock , can any one help ??