I'm new to this, but I'll explain my problem as best I can.

My '93 sounds like a machine gun is firing under the hood when I come into a stop. Upon braking, the entire dashboard shakes badly and I can feel the entire front of the car shuddering the last 100 ft of the stop. It seems to do it after it is warm. My mechanic has had it for a week, and it won't do it for him ever, so he thinks nothing is wrong. I even tried driving it with him in the car, but it wouldn't do it. Other than that, the car runs fine as long as I don't have to brake. It has 80K miles on it. Any ideas as to what could be wrong?

Obviously, this problem is a bit too complicated for this forum. Don't worry, it stumps a lot of people.

Obviously, this problem is a bit too complicated for this forum. Don't worry, it stumps a lot of people.

Intermittant problems are diffcult to diagnos..If the car won't act up, its kind of hard to fix.
if this was a constant problem, I would lean towards a pulsation issue caused by excessive thickness variation, rotor runout or warped rotors.
Unfortunatly we cant hear the noise or feel the dash shake to give you any ideas.

do you have any brake fluid on your pads?

The problem may not be with you're brakes at all. Do a web search for TCC Solenoid lockup problems. You will find that the torque converter clutch (TCC) solnoid is locking up and not allowing the tranny to unlock itself from direct drive from the engine. This puts great strain on the motor (thinking its in 3rd gear on deceleration) and causes the motor to shake and studder, most likely weakening the motor mount bushings and causing metal on metal slamming. You're lucky it unlocks when you stop. In most cases, mine for one, the TCC will remain locked, when you stop, and it'll stall, not letting you put the car into gear. It still thinks its in 3rd. Heat is the ultimate factor. It only happened to me after 10-15 miles. I had the TCC replaced ($12 part $400 labor) and had no further problems. Im sure a backyard mechanic could do it cheaper.

Yup, I think techman's got it. You can disconnect the lockup solenoid on the front side of the tranny case, to see if the problem goes away. The TCC only engages above a certain speed, and under specific load conditions, so if your test drive isn't taking you somewhere you can cruise on flat road at 40mph+ for some distance the TCC won't lock up, and you won't feel it shuddering while trying to unlock as you slow down. You can look at your fuse diagram in the owner's manual and see if there is a dedicated fuse for the TCC and pull it out for testing purposes, too. Doing so will likely light the Check Engine light, but you can clear that after determining if the problem is gone. The drivetrain will operate normally with the TCC disabled, but your cruising mileage will drop by a few MPG, otherwise you won't notice any difference.