The question is far too vague for me to give any kind of meaningful answer. Take it to a garage that services Subaru and describe the problem to them. This is a complex system with many parts and one or more of many things could be malfunctioning.
The 2001 Subaru Outback has 16 valves.
The 2001 Subaru Outback is a gas-powered vehicle.
The 2001 Subaru Outback has a 5-speed manual.
The 2001 Subaru Outback has a flat 4 engine.
The 2001 Subaru Outback's turning circle is 36.7 ft..
The height of the 2001 Subaru Outback is 5 ft. 2.2 in. (62.2 in.).
The 2001 Subaru Outback has single overhead cam (SOHC).
The 2001 Subaru Outback runs on regular unleaded.
The 2001 Subaru Outback is 15 ft. 7.4 in. (187.4 in.) long.
The 2001 Subaru Outback has 40.2 in. of front head room.
The 2001 Subaru Outback has 51.3 in. of front hip room.
The 2001 Subaru Outback has 53.6 in. of rear shoulder room.