Hi, I have a 1989 90 county and its been great but the past few days i've had an issue with it, after driving along fine for about 3 miles i started to hear a strange noise from the engine it was a cross between a whine and a blowing sound, there was a lot of crap pouring from the exhaust and a complete loss of power, after a few coughs and farts it seemed to clear and drive fine. its happened a few times in the last few days, does anyone have any idea of what it may be???