How do I fix this?
 

My new jeep has recently gained a hi iddle, and the brakes have gone rock hard and seem to work last minute. All of this has happened all at once. Any thoughts? thanks.

Sounds like unrelated issues.

I'm not completely sure about the brakes without more info, but it sounds like there is an issue with the master cylinder brewing.

The fast idle could be several things. You need to see if there are any MILs being thrown. It is possible for there to be codes without a CHECK ENGINE light coming on. That's where to start first.

if u do have an 86....check for vacuum leak. mine was tube from sensor to throttle body. same symptoms.

Check for vacuum leaks, generally, if the force applied to the brake pedal needs to be increased dramatically for what seems to be minimal braking, the power brake booster is suspect.

The high idle may also be caused by vacuum leaks, start your search there.

check the vacuum booster tube that goes from the brake booster to the intake manifold. that is usually the cause of a stiff brake pedal. it may also be the cause of your high idle.

This^^, happens everytime I seafoam. I pour the seafoam into the intake through the Booster hose, and forget to hook it back up.

Sorry guys I failed to mention this is on my new 1990 xj.
Any how, now the "check abs" light is on... What do I check??
When I drive the brakes are now locking up. I have only driven around the block in it a few times.

Vacuum vacuum vacuum.

Agree... vacuum leak cause high idle vacuum also powers the brake booster.