I have an 89 Integra LS Coupe. It has a 5 speed, 1.6L, 180K. Strangely when at a stop and I have the brake depressed it causes my idle to drop from 650 to a rough 450 rpms. When I release the brake the idle raises back to 650 and the idle is smooth. Has anyone ever heard of this happening? The car doesn't die, but just idles poorly. Beyond just the braking issue the car runs great. Thanks

 

My idle drops whenever I do anything with electronics in the car. Brake, turn the wheel, open or close the windows.

 

Your brake booster may be suffering...

 

Yep, noticable drop in RPM's was a warning sign my vacuum booster was failing