Hi,
After my Jag has warmed up I get a horrible rattling sound when giving gas going up a hill or if I am coasting and then give gas. It sounds like two tin cans rattling together. I guess it could also be described as a pinging noise?

I have tried various high octane grade fuels and have done three fuel treatments to see if that would make a difference. But it hasn't.

Does someone who is more mechanically inclined have any idea what this could be and if it will be an expensive fix?

Help!

thanks for reading...

 

Is the check engine light on? If so, need the codes.

The word 'rattle' has often been used regarding failure of the cam timing chain tensioners but more often at start up than running. That problem does not set a code until failure. If you have no record of the tensioners being changed and if, indeed, you are hearing a chain rattle you are at the point of destroying the engine. From your comment on mechanical skills I would suggest that you get the car to a qualified mechanic yesterday morning. Towing should be considered. Cost could be expected from US$800 for an independent to US$1300 at a dealer.

Hopefully, it will be something much more simple but you must eliminate that possibility now. Search 'Tensioners' for lots of sad posts.

 

Hi,
Thanks for your response. Engine light is not on and when the engine is cold there is no rattling noise.

The chain tensioners are not upgraded and I was planning on doing that next year. They did look at the easily accessible tensioners to see what condition they were in and the picture and comments from the Jag repair person were positive. I.E. they looked like new and based on the low km's he said it should be addressed but wasn't urgent. But I guess who knows if the lower ones are bad?!!?

I am just hoping to get some knowledge before the car goes into the shop on Monday and they check it out.

 

While there have been reports of primary tensioner failures the vast majority are the secondary ones. Unless the 'shoes' are missing you simply cannot see a failure, which is normally a crack in the housing, without removing it.