Mazda Repair: protetge dies with hard stop, shunt mode, light flicker

Question
QUESTION: We have owned a 1990 Protege since it was brand new.  It has only 114,000 miles on it.  The car will stall out and die with a hard stop.  I can do it on command.  Go 30 miles an hour, hit the brake medium hard, and the engine light comes on.  Car dies.  Sometimes it almost dies and I see the engine light flicker. There is a hole in the muffler, would this contribute to a stall?  Tuneup was doneat 90,000 miles.

ANSWER: Is the AC on/off?.  The ICS (idle control solenoid) holds and stabilizes the idle speed for drag caused by the AC compressor, the alternator and the power steering pump (if equipped).  If this solenoid has failed it could contribute to the stalling situation.  Exhaust restrictions usually contribute to power loss or inability to achieve higher RPM speeds.

---------- FOLLOW-UP ----------

QUESTION: AC is off.

I tried an experience.  If I do the same braking with the car in "neutral" it will not stall out.  Could it be a vaccum issue?

Answer
It's a good idea to check for a vacuum leak however when your in neutral the motor does not have the load of the transmission so it may not give the same fault.  Vacuum should be 12-17 psi/hg at idle if you have access to a gauge.  Leaks are also fairly easy to hear. (hissing or a whistle)

With the engine idling, all accessories off,  switch on the AC.  Does the RPMs slow down or stumble or is it stable or does it increase slightly. (assuming the AC works).

Check some basic things first.  Idle speed and base timing (note this must be done with the computer in shunt mode or it will correct for your adjustments) (timing best at 12 deg BTDC, idle set to 800RPM) fluid levels and air filter.  Also a good cleaning of the throttle body can clear up simple drivability issues.