bit of a strange one, i can be running and suddenly the engine will loose power, if i put foot on clutch the engine will fall to a stable idle but will not accelerate any higher.  stop, switch off and on, restart and it'd fine again, some times there's no fault code, sometimes it gives a manifold pressure fault, i've tried for any loose connections but can't find anything, don't believe manifold sensor is at fault as it's an intermittent fault 

 

any ideas ?

What engine, petrol/diesel and type.

 

DB.