I own a 1982 S3 N/A which runs very poorly when hot.
The symptoms are as follows:
1) Starts from cold relatively easily and picks up well on the throttle with no flat spots.
2) Continues to run well up to temperature and also when the fans cut in, albeit as the temperature rises the idle drops from 1000 revs to about 850 revs.
3) Turn the engine off and leave it for 5 to 10 minutes and it is then difficult to restart, runs poorly and eventually dies.
And so something is breaking down in some way due to heat.
I have checked and or replaced the following:
a) New speak plugs.
b) New distributor rotor arm.
c) New electronic ignition module (Accuspark).
d) Distributor cap, HT leads and plug caps are less than two years old during which time the car has covered less than 2000 miles.
e) New ignition coil and ballast resistor.
f) New inlet manifold gasket.
g) Carburettors ultrasonically cleaned.
h) Carburettors balanced with Morgan Carbtune.
i) Compression checked 170 psi for each cylinder +\- a couple of psi across the four cylinders and so I do not think that the engine has worn piston rings, cylinder bores or a blown head gasket (no “mayonnaise” in the oil filler cap).
j) Vacuum hoses from the inlet manifold do not seem to be leaking.
k) New fuel filter.
So, I have run out of ideas!
Question - what have I missed?
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