95 Avalon

Cranked up a 95 Avalon today and heard a rattling noise in the engine. It appears to be coming from the upper part of the engine. Any ideas on what is causing this?

Lifters, rocker arms, valve springs for a few. Not a problem if it just happens now and then. If it's a regular occurrance, change the oil and filter and see if it goes away. If not, could be low oil pressure caused by a weak pump or a bad component in the valve train. Connect a direct pressure gauge at the sender unit port to verify good pressure. Don't trust the idiot light.