JAGUAR ENGINE POOR MILEAGE

My 2.0 Diesel X Type Jag Is Only Returning About 36 To The Gallon. I Think There Is Something Wrong With It As I Don't Drive It Heavily And...

Car Is Idling Roughly And Uses A Lot Of Gas. I Use Premium. Have Had Spark Plugs, Air Mass Sensor. Eight Rubber Boots But Not Coils And...

The Vcm Code Is 77, Fuel Failure, On My 1994 Xj12, 100050 Miles. 6.0l The Manual I Have Does Not Cover That Code. Can You Tell Me What It...