i have a 91 accord lx that has a bad idleing issue. when i start my car to warm up the idle is at apporx. 1200. then after it is warm, it drops down to about 400 and sometimes lower. the car runs rough also after warming, and sometimes stalls because the idle is so low, sometimes at 100. does anyone know the problem?

 

I think you might be able to adjust your idle speed with a little screw. I will be on the left side of your throttle body(as if looking under the hood). You have to have your engine at normal operating temperature, idle speed should be at about 500 to 600 rpms, and if you drive an automatic it should be in park or neutral.

 

It sounds like you've got a vacuum leak somewhere in the engine compartment. Listen for a hiss.
Another way of locating a vacuum leak is the use of a can of Carburetor Cleaner.
Attach the little plastic nozzle extention and spray in small areas where you suspect there might be a leak. If you're right, the RPM will rise when you spray.

If you've had a prior Brake MAster Cylinder failure, and the Engine now stumbles when you apply the brakes - you've a bad Power Brake Booster; and it's causing an internal vacuum leak.

P

 

get tune up, first, before making any adjustments... This could also be an internal problem since your motor is aged. Purchase a shop manual...it has trouble shooting sections that will help you.