Has this problem come about or has it always been there?

if plug changing cured it then probably it is a spark fault.  A new plug can
fire on a lower voltage, once running you don't need such a strong spark and
the warm plug fires on a lower voltage too.

first check should be spark voltage, if low then that should be checked and
the problem located.
if not low then I would try and find what makes it start, for instance has
it got a vacuum leak which can be counteracted by a richer mixture.

the second accelerator cable is probably from a cruise control , if not then
there are other possibles.

mrcheerful

First have the coolant temp sensor checked. Sounds like its not actually
telling the ECU the engine is cold, so its fuelling for a hot motor.

Tim..