idle pulse with brake on!?

[toy-YODA jedi]

My 90 toyota 4x4 v6 idle will jump back and fourth from 900rpms to 1500 rpms when im am sitting still with the brake on. Only does it with the brake is pressed.

Also when it is surging like this my power steering drops out . is this a result of the low idle or is the P/S have an effect on the vaccum?

[burger]

welcome,Jedi.Now,warm up your truck.then adjust your idle screw(big flat one on the throttle body) so that your truck idles around 800-850rpms(whichever you prefer)Listen to your problem dissapear .

[greasyjeep]

Also look for vacumme leaks

[Toy Sport 4x4]

Vaccum leaks and a misadjusted throttle position sensor are some of the most common for this problem.