Ping on XJ8 1999

1999 XK8 Jaguar has rattling sound when going up steep hills or when tank is low. NOTE ? this didn?t start until the transmission was replaced in 2007. I have been to the Jag dealer after $900 still making sound, went to my regular Jag mechanic and paid $700, but they can’t find cause ether. Old cars do wear out but this one looks to good to drop.

All suggestions welcome.


What did they check?

This sounds like pinging from here. Possibly due to lean operation. Possibly due to a weak fuel pump. That would be affected by the tank being low, because a weak fuel pump could need the “head pressure” of the fuel’s weight to assist it. And it could be incapable of meeting the engine’s needs on a hill.

Did they check for stored codes? There should be some.
Did they check fuel pressure?