I'd like a crack at this one, professor.
1) Since our motors have such *interestingly* designed intake manifold/port
systems, let's say that fuel atomization is less than optimum. If the
weather's cold, let's say it's just a little worse. (I'm no physicist, I'm
guessing here - y'know how cold stuff turns to vapor slower than hot stuff?)
2) On any MGB, instead of a throw-out *bearing*, you have a throw-out carbon
block. It manages to do the job, but it does introduce some friction when
you shove the not-moving block against the rotating clutch bits. So the
slowing down is annoying, but normal.
3) I'll bet your brother's '78 has one of those brake boosters, yes? Since
it works on vacuum supplied by the engine, I'm going to guess you have a
little crack in the diaphragm of the booster. Now when you press on the
brake pedal, (and only when you press on the pedal) you introduce a vacuum
leak.
Since brother's car already has condition 1, it's not running at its best.
When you add either condition 2 or 3, the engine stumbles, but has enough
juice left to keep running. When you have all three conditions, it's enough
to stall the poor thing.
That it has a hard time coming off throttle bears up the vacuum leak.
You're plowing along with the throttle open, so there isn't so much vacuum.
You flop the throttle closed, and now the engine is really sucking hard
against the throttle plate and any other place it can get a breath. Your
vacuum leak is now introducing a greater load of air without fuel. Mixture
gets very lean.
I'm too old to think I know it all, but this is sure where I'd start
looking. Can you remove the brake booster vacuum line (and plug the
fitting) and take it for a drive?
Matt Kulka
Huntersville, NC
'74 B
-----Original Message-----
From: Jurgen Hartwig [mailto:gt0003a@prism.gatech.edu]
My brother's '78 MGB is a little sick...
After the temps started to drop this past December, the car began to
have problems with stalling. It drives perfectly fine at speed, but
when you get out of the throttle AND put in the clutch and brake, the
engine stalls...
|