Orig set up, power brakes. I have had the car for 2.5 years now. Since I have had it I have seen no leaks, nothing on the ground, nothing wet on the rims, back of rims, at the wheel cylinders etc, no brake fluid leaks, level in resivor stays the same. Since I have had it it stops fine. Panic stop is fine. No hard pedal, no sponginess. The thing I do see is when I stop at a light and I am sitting there for a bit the pedal will drop a hair (not close to the floor) then hold there just fine, car does not move. I find the dropping of the peddle odd though. Is this a booster leak? Maybe put a new hose from it to the intake, it is old and hard as a rock. this car has a miss that I can not get rid of. I have read up that a booster with vac issues could cause a motor to misfire.
When is the misfire happening? If you can replicate it at idle in park, then start plugging off vacuum lines and accessories that use vacuum. Your master cylinder may have an internal leak that allows the fluid to go around the piston up to a certain point, and then seals...stopping the pedal from dropping further.
The misfire is always there, idle, under light load driving down the road/hwy, under load I don't feel it. If I up the RPMS by hand at the carb the motor runs rough through the rpm range I would hit.
"When is the misfire happening? If you can replicate it at idle in park, then start plugging off vacuum lines and accessories that use vacuum" Doing that tells me what?
Helps you find the vacuum leak! As you disconnect and plug things the mis-fire might go away. You can also use a piece of hose held to your ear with the other end sweeping the connections looking for a hissing sounds while the engine is idling. Check the carb base gasket also. If you cannot find any vacuum leaks and the vacuum, gauge looks good (as per Larry above), your ignition system is the likely next candidate (ie pull plugs and look at them). With regard to the brakes, I like Adams theory above. a small pit in the master cylinder bore might allow the pedal to move when applied as the fluid leaks by, but them becomes good again as the plunger gets past the pit.
There you go, parts changer mentality instead of testing and finding out the cause. I predict a lightening of your wallet and increasing frustration., and this thread going to 3 pages in no time.
If you are referring to what Adam stated above and I mentioned, that isn't the booster. Either way, trouble shoot and fix your misfire first, maybe the brakes will fix themselves. This is possible.
