idle problem

[nberry]

i have 1990 pickup 4x4 v6. when i apply the brakes and the engine is idling the idle speed starts to jump up and down. when i release the brake idle goes back where it should be. if anybody has any ideas on this or can point me someplace else i would appreciate it.
thanks

[mustang67408]

Originally Posted by nberry

i have 1990 pickup 4x4 v6. when i apply the brakes and the engine is idling the idle speed starts to jump up and down. when i release the brake idle goes back where it should be. if anybody has any ideas on this or can point me someplace else i would appreciate it.
thanks

Make sure the coooant level is topped off and this is usually a bad or out of adjustment TPS (Throttle Position Sensor). It is located on the throttle body and is adjustable with the correct tools. A multimeter is usually needed.

[theyotaguy]

Turn the air screw on the throttle bod y back in.

[azredliner]

Originally Posted by nberry

i have 1990 pickup 4x4 v6. when i apply the brakes and the engine is idling the idle speed starts to jump up and down. when i release the brake idle goes back where it should be. if anybody has any ideas on this or can point me someplace else i would appreciate it.
thanks

Bad vacuum booster? If the booster is faulty then when you apply the brakes it will cause vacuum to leak and the engine will idle irradicly.