The car was running fine, after a few short trips 30 miles or less over a few weeks it began to break up while driving. Sometimes it would take a bit for it to start up once turned off, but then id go for a loop (3-4 mile drive) and about half way it would begin to break up under load. It would idle fine, drive just fine up until that time then it would get worse and either shut off or not restart if i shut it down. I cleaned the carb, changed the plugs, installed a new fuel filter before the carburetor. I did notice a couple of the spark plugs had come out by hand using no force, one of which i was able to lift right out without turning....... what is the easiest way to repair the threads or get these plugs to stay in...... i believe this may be the cause of my breaking up issues. If anyone can assist it would be greatly appreciated. Thank you.