Alright, so I got a 91 Honda Accord and the brakes are messin' with me. Sometimes I have no issues and they work fine, other times it feels like they have air pockets and I have to ram my body weight down to make the car stop. The brakes have been bled several times to make sure now, the calipers and pads are new, and the rotors are good, so I have no clue what's going on.....any ideas?

 

Does the brake pedal seem hard to push?
That might lead to booster or booster vacum problems.

Does the pedal sink to the floor?
that might lead to a bad master cylinder.

 

If you hear an associated hissing from under the dash whenever the brakes go hard, you have a Brake Booster issue as Hondadude suggested.
It's rare, and most time associated with either a present time Master Cylinder failure or one which occured in the past.
I would suggest a complete inspection of the booster vacuum hoses for any which might be leaking to start with.

P