idle changes when the break lights come on but not always , also some times the oil pressure gauge flickers couldit be a bad earth ???

 

sounds like a bad earth to me. try giving your battery a good charge and see if that helps. also check the condtion of the battery. cold weather seems to kill old and aging batterys pretty well. if the battery is on its way out then the alternator has to work very hard.

Rich

 

The idle will change, as the servo gets it's vacuum from the engine, so just using the brakes wether standing still or driving does indeed alter the air the engine is getting.... thats the simple version.....
the gauge may be due to a bad earth....

 

The servo uses manifold vacuum but only one slug for every application.
If the problems are there when the brakes are held on without pedal movement, it sounds like a split servo diaphragm or other servo problem.
The easy way to check is disconnect and plug the servo vacuum hose then try again. Don't drive the car like this without trying the brakes first. The pedal pressure needed to stop will be MUCH greater.

John