Apply brakes....RPMs drop

[Dieseler]

1989 SR5.... this only seems to be random when brake pedal applied the RPMs surge this has happened at stop lights with the brake fully pressed when I release the pedal the RPMs are normal.
What is causing this pulsing surge of the RPMs.

 

[arndog123]

Make sure your idle speed not set too high. IIRC, it's supposed to be 600-700 rpms. Having it set too high will cause the rpms to surge when pushing the brake pedal. Check your brake booster and associated hoses too 'cuz they might be leaking.

 

[Dieseler]

When I start the truck cold the RPMs runs higher than I am use to, I assume 6-700 rpm is on a warm engine , if my idle is to high how do I adjust it down my mannual I have is very vague it covers several engine types and I can't narrow it down to the 6 cylinder motor idle adjustment.

 

[Doable]

Does the Toyota have a brake boaster ? Like in the previous post check it . If it does you can block off the line from the intake to the boaster to rule it out. My 4Runner acted the same way on its last trail ride and the boaster was the culprit.

 

[toy4x4runner]

Does the Toyota have a brake boaster ? Like in the previous post check it . If it does you can block off the line from the intake to the boaster to rule it out. My 4Runner acted the same way on its last trail ride and the boaster was the culprit.

Same hear. Thats how i learned how to break and gas at the same time with my right foot. I was young and it took me a long time to figure the problem out.