Rattling

[lsownerof2]

Hey guys, this forum is great!!! bought 2 ls 400's in the last 3 months and this has been a life saver!!!

I am having a rattle coming from under the engine when I am on the gas...any ideas what that might be? Any input would be helpfull. Thanks!

[Vern Dias]

Are you are using premium grade gas....

If not, you need to be. Most likely, you are hearing detonation caused by too low an octane rating.

Vern

[larryp]

You didn't say what year the LS is - but i doubt it's gas. I've run nothing but regular in my 91 for 4 years and it never pings. Sounds more like something is loose in the engine compartment. Might try having some one rev it up while you look and listen.

[nc211]

this sounds like a heatshield on the upper converters have come loose. If it's a rattle, then just ping around underneath until you find something loose. My guess....heatshield has come loose... it happens.

[lsownerof2]

Sorry, its a 1993 with 162K on it.