I recently took my 1991 1.3 Polo to my local (non VW) garage as it had
begun
to overheat after a very brief run.  I drove the car to the garage
(about
one mile) and, despite the short distance, the car was driving fine.
I was
informed the overheating was 'just due to a loose connection' for
which I
was not charged.  On leaving the garage the car began losing power
under
acceleration (particularly in first gear), resulting in me having to
drop
down gears and/or attempt to drive at a consistent rev level.
Dropping down or decelerating resulted in the car picking back up
again.  In addition, moving off
from a standing start was almost impossible resulting in me having to
slip
the clutch whilst maintaining consistent revs.  Despite this on a
couple of occasions it just stalled.  I took the car straight back
whereby the mechanic drove the car and agreed something was amiss.

I have now been informed the problem is
'probably the ECU'.  The car was sent to a local electrical auto
specialist
who could find nothing wrong with any electrics other than to suggest
the
above.  The car has recently had a new distributor (circa 12 months
ago)
which I am told has tested OK as have the other likely mechanical
'culprits'
(I write this as someone with little knowledge of engines).  The
garage has
suggested they source a second hand ECU assuming they can find one to
match
to check if this is the problem.

Aside from the overheating - which only happened once and
was not severe - the car is generally solid and had been running
perfect
prior to taking it in.  From a layman's point of view it appears that
the
problem has resulted from something which changed whilst in the garage
but
I'm willing to accept it may just be a co-incidence.  I'm happy to
stump up
£50 for a second hand ECU but would appreciate your views on the
likelihood
of this being the problem.  Finally, I drove the car back from the
garage
prior to the weekend and it was performing better than when I first
reported
the problem - although it wasn't great it didn't come close to
stalling.

I appreciate, even as a layman, that it could be a number of things.
However, would an ECU problem result in varying performance or would
you expect to see the same'ish problems whenever it's driven?  I've
had the car for many years so if you need any more info please ask.

Many thanks