So, I'm a little stumped here on this one. My 1989 FC Convertible Non-Turbo/manual-Trans starts surging at idle once i run it hot. Used carb-cleaner to try and diagnose a vacuum leak and the surging only stops for a few moments after spraying the main fan/water pump pulley. What is really odd is that the surging also stops immediately after I turn off my headlights, starting to surge again the moment I turn them back on. Could all this just be a bad water pump? The fan is stiff when I try to wiggle it around. All ideas more than welcome!

 

Try adjusting the Throttle Position Sensor (TPS)..you can find threads on that subject in the SEC Gen Specific section (use Search..it helps).
Your Fan has nothing to do with the Water pump as it is Attached to the Water pump.
If the Clutch in the fan doesn't work you would know.The car would most likely show signs of overheating.

 

Thanks for the info! Will check it out, and use the Search. I tried using the "Search" several times before posting here in hopes that someone else had the same issue with the pulley/headlights/surging connection, but found nothing. I looked at the TPS several months ago when the surging first appeared... I had driven the car at 110mph for 90 min straight and it's been surging ever since when I run it hot like that; but I never got into adjusting it, just cringed at spending $400 for a new one and was trying to look at everything else in hopes of a cheaper fix, ha!
The leak at the main pulley is the only reason that had me thinking something with the water pump; but there is no overheating issue at all. Thanks again mate