This has been happening to me and the only other definitive time it did was when the exhaust manifold cracked and sheered off just below the bolts on the engine. The oxygen sensor mounted just after the first curve went nuts. Check engine light lit. When I mounted a new manifold the light stayed lit for awhile and now it is intermittent. It drives me crazy. Everything on the motor checks out and it IS a very simple engine, mechanically. The biggest snafu will be oil or lack of it and that has its own lamp!
What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.
