Am recent owner of 2002 LXT w/ 5.4l. Bought car with very low mileage (less than 50000mi). When hit 50500 got "service engine soon light. Per owners manual: verified not out of fuel, checked fuel cap, put some 89 oct gas in, and just did three drive cycles (can't go over 50 mph here). Light still on. Any ideas why? I assume "soon" does not mean "immediately".