My 81 GSL is missing at high rpms in 3rd and 4th gear. I have switched the coils so i know its not that. I was wondering my guess is it could be the fuel filter. Any other suggestions.

 

Get it fix. Seized my motor and had some of the same symtoms.

I changed my filter on a reg basis because of the age of the tank. Could be your problem. Float may also be stuck on the carb.

Someone mentioned that it could be the distributer, or the thing inside the distributer (don't know the name because I'm stupid).

It took a little while on mine i guess but the leadings were not firing, so check or change your plugs and wires if you have not, but don't let your car know that.

That is about all i can think of. I would get it fixed soon though. Again that is what my car started with about 3 or 4 weeks ago.

 

check the fuel filter. and check for vacuum leaks. you can figure out how to do this by searching.