I have a 2001 Cherokee 4.0 when I start it it instantly revs up to 2,000 rpm and stays there what could cause this it popped a code for a large vacuum leak but I cant find it
any help would be much apricated

 

The large vacuum leak is the source of the problem. The engine is taking in more air than it should be. That causes the engine to run out of control.

Find and fix the leak.

 

Has it had any recent work done to it? Manifold gasket? Vacuum line replacement?
Is your intake manifold missing any bolts? Are any bolts loose along the top of the intake manifold where it meets the head?

 

Your code "large vacuum leak". Was it actually "large EVAP leak" or a code for running lean?

In both cases you need to fix it to fix your problem but knowing which it is would make diagnostics easier for people.

 

If you remove the intake tube then cover the throttle body with your palm and the engine does not stall, you have a large vac leak. Doing this may also make the leak easier to locate.

 

it came up with a po455 code i think that should actually be evap?

 

Yep. So IF the code and your high idle are related, which is not necessarily the case, you need to look for EVAP system leaks....... but even if they aren't related you still need to fix the evap system leaks.