the idl is good till i step on the break. it idles up and down. dont know why it doing this.

 

could be your power booster.

 

Idle is set to high... When you step on the brake the ECU thinks your coasting to a stop and is shutting down the injectors to save gas...

Lemme guess its sounds something like this.... Vrrooooom Baaaahhh Vrroooom Baaaahhh Vrroooom Baaaahhh....

 

^^^ this is the problem.

my 4x4 did the same thing. i turned the idle down just a little and it fixed it.

maybe you have a slight vacuum leak that has caused the idle to come up, and that is causing it.

 

i solved the problem yesterday; i left it running and placed a brick on the brake.
it started doing the VROOOMMM BAHHHHHH jeje so i turn the screw on the AFM censor counter clock (the screw went up). it worked but the A/C blew warm air so i had to mess with the screw on the thr.body and like magic. hope this works to anyone with this problem....