I have a Mk 3 from '68 which is a tired old nail but provides plenty of
entertainment through the summer & recreation through the winter. It's
had a problem for some time which is getting a little worse & beginning
to be a pain, so I was wondering whether anyone out there could help.
After 20 miles or so, once the engine is good & warm, it starts to
misfire. This will happen at 20 or 70 and happens mainly when
accelerating: power is feeble, the engine note becomes wetly flatulent
and there are noisy backfires, sometimes out of both ends. After maybe a
minute of accelerating on full throttle, say up a long hill, and
complaining all the time it sometimes clears its throat & goes OK while
the throttle stays wide open. This started a few years ago on very warm
days (75f is very warm to me) after 40+ miles but now it's becoming too
frequent to ignore.
Things that have been changed without stopping it:
Coil, Leads. Plugs, points condenser (several times). Distributor & cap.
Fuel pump. Fuel lines (& tank cleaned), the line from pump was
insulated. Carb needles & jets, floats & valves (set for height,
synchronised, check the pistons are free moving, have oil etc etc.). The
block and head have changed twice, as well, in that time.
Any ideas?
My feeling is that the problem is with the carbs, as it's a misfire and
they are the only thing which hasn't changed. But, I'd like some
confidence before splashing out on new ones at half the value of the
car. Not that I'm tight or anything, you understand.
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