My 1991 Loyale Wagon sat for a month in the garage and the first time I started it the engine reved a bit high, maybe 3000 rpm and I heard a loud valve tapping noise that went away as soon as I tapped the accelator which brought the rpm down to normal. It drove OK for three blocks then had about an eighty percent power loss and it also idles very rough. The engine stumbled and ran very rough as I drove it home. There is no smoke coming out the exhaust.
Any ideas what the problem is? It has 150,000 miles and had been getting excellent gas mileage and not burning oil.
Bill