My 1993 Cadi has been sitting idle for four years without being run. After much effort, I got it up and running with much pooping and gagging. After copious use of fuel injector cleaner it improved markedly. However, it still doesn't run as it should and only gets 11.3 mi per gallon going downhill with the engine off. Can you help?

Seeing how we don't get to see what other recommendations have been given to you already, could you answer this for me. What, other than injector cleaner added to system have you done? Was fuel tank removed or at least inspected for rust inside? Were fuel lines flushed at all?

Hi, this fuel delivery system is in horrible shape. i recommend replacing the fuel pump and filter if not done so already. i would also advise to check the air filters integrity as well. replace if needed.Another area of concern will be the fuel pressure regulator. due to the sit up time, the diaphragm may have become stiff or ruptured. this will cause poor economy as well. have it replaced if possible. Next will be the basic tune up procedure. Have the wire set and spark plugs replaced as well. spark plugs can become inefficient during a four year layup period. it would be wise to have these replaced along with the wire set. this well restore the economy immediately. Lastly, i would advise to inspect the injectors. make sure the PCM outbound voltage if proper for maximum pulsation.

Oh, one more checkpoint. Inspect the PCV valve for clogs and the intake manifold gasket for damaged as well. If these two components are damaged in any way, it will affect the economy and idle dramatically.