My 2000 XJ started making a knocking noise it only does it when I put it in gear and start driving down the rd and it only lasts for a few seconds and then it's gone until I shut the motor off and then it starts all over again it doesn't make any noise in park or neutral only when I put it in gear and start driving

 

Do a search for flexplate bolt. Also do a search for piston skirt.

 

Wouldn't it make the noise in park to if it was a piston skirt or flywheel not just when it starts down the rd and only for a few seconds before going away it also only does it in forward not at all in reverse any help would b great I am supposed to go on vacation 2nd week of June and would like to get it fixed by then thank u

 

Anyone have any ideas for me

 

Remove the inspection cover and check the flexplate bolts, see if any are loose. It'll take 30 minutes. Not unusual for them to make noise under certain conditions but not others.
Unlikely it's a piston skirt if it goes away completely in just a few moments.

 

Thanks I'll check them tonight

 

You said it does every time you start. Is that after engine cools off?
Piston slap is normal on the 2000 and go aways very quickly. Like in 100 to 500 feet as pistons warm up and expand. Piston slap is often only heard under load too.

 

It does it every time even if the engine isn't cooled off and it only does it when I'm going forward never in reverse and I even let the motor warm up for half hr before driving it and it still did it

 

My 2001 was doing this after I got it, turns out the fan shroud was not locked in on the bottom and the fan was hitting it just for a few seconds after take off. Not sure why the fan clutch was engaging when cold but that's what my noise was.