today on the way home i had the problem of my car loosing RPMs whenever i touched the brake not only when i slowed down but even pressing it ever so gently for just the brake lights to come on there was no problem when i was letting it coast nothing happened only when i hit the brake did the RPMs start to go down

 

Do you have a vacuum booster or manual brakes?

 

manual brakes

 

Sounds like you have an electrical/charging/battery problem.
What happens with the turn signals? Does the engine RPM drop in concert with the turn signal flashing?
Also what kind of battery voltage are you reading, engine off and engine running?
Time to break out a good meter and start looking.

Good luck,

Scott

 

well im pretty sure cause i had just put a new battery in before i had left and i put a new alternater in like 2-3 weeks ago


all of the electrical components under my hood have been replaced within the last 14 months

 

There is a big difference between "pretty sure" and "I have tested these items with the following results".

Good luck,

 

i know but i dont have any of the testing equipment my moms boyfriend does but thats where i was coming from when i had this problem and i dont wanna drive 8 miles there with this happening expecially on a road with alot of stop lights and a decent amount of traffic

 

If you are going to own and operate a classic Mustang, a good Multi-Meter is a "must" tool you need to have and know how to use it. Don't bother with the cheapos....go ahead and fork out the cash for a "Fluke" 75 series multi-meter.
Try going through some basic tuneup procedures of checking the fuel filter to see if it is clogged, then tweak the carb so it is breathing properly and the idle adjustment screw is adjusted correctly. Check all your vacuum hoses and electrical ground connections, especially the one from the battery to the engine. Get that multi-meter. You need to know how much in coming out of and going into your battery, and you need to know how much is at the coil.

 

well as long as im not pressing the brake idle stays at 1400 which is where we set it at i will check the connection from the ground side of the battery to the engine the fuel filter is new and if it was clogged wouldnt it be doin this all of the time and ill also check the only vacuum hose i have all the others r blocked off

 

So If your in park and the engine is running and you hit the brake, the RPM'S drop??? Im with Scott on this one, Check the charging system. Does it still start up strong? or sound weak when the starter is turning over?