My son has a 1.4 Citreon Saxo West Coast. Two weeks ago it developed a fault with the engine revving higher than normal. It was plugged in and no fault found. Since then, all sensors have been removed and terminals checked. Now when you start the car, it has problems ticking over and stalls alot. If you hold the throttle down slightly, it will run but the revs go up and down, like it is hunting. Any ideas as to what it can be as no fault can be found on the plug in. Thanks in Advance