i have a sportrak 1.6 el 1990 carb model.
its had this awful starting and running problem for ages.
( starts on the button then coughs and splutters after that
sometimes for ages sometimes for 5 mins.)
ive replaced ,
plugs, points,distributor cap , leads ,stripped the carb 3 times.
Then i spoke to D & G CARBURETTORS in nottingham thinking the carb
needed replacing,
he told me to look at the carb cooling system and vacuum pipes.
when i checked the vacuum pipes , quite a few needed replacing
especially on the junction near the ditributor.
then came the crunch , all the small water pipes were full of crud.
I followed them all over , and came across a small brass
thermostat valve directly under the inlet manifold , beneath the carb. It controls the water temp in the inlet manifold and auto choke system .
It was completely knackered , even to the point where the
connection to the water pipe had snapped off and sealed itself with
rust.
Got one from DIAHATSU MAIN DEALER in japan , 2 weeks later it came.
Its now fitted .

AND RUNS LIKE A DREAM.

just thought i would share my experience with fellow members
in case anyone else is struggling to find an answer.