1990 Honda CRX Unknown

HONDA CRX-HF, averaged over 53 mpg for 299000 miles according to complete fuel and maintenance log. At times, the on board computer beeps on trailing throttle. The injectors might be dirty, but it doesn't seem to affect performance, so I ignore it. New alternator and water pump, the last installed as a precaution when changing timing belt. The engine has never over heated and valve lash has never gotten out of spec. This is the most reliable car I've ever owned, and among the very best that Honda made, but I now find myself with three cars and something has to go.