back fire on 1994 Jaguar XJS

backfire at low rpm ,also will not rev from an idle,sputters and backfires. changed fuel pump,filter,mass air.

Asked by for the 1994 Jaguar XJS
Crank shaft position senor failure on that model can do this as well but proper tests for vacuum leaks and looking at key sensor values on an oscilloscope may show what the true problem is.
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I would have the catalytic converter inspected for a possible restriction. Also check for any vacuum leaks or an air leak somewhere.