2002 Blazer Idle Problems

When cranked a loud clanking rattling noise emits from my engine. It only seems to be able to really be heard when I'm idoling when I put it in drive and press the gas and go it dies down slowly and afte a little while it slowly subsides but is still barely audible. What could it be and how can I fix it?

When cranked a loud clanking rattling noise emits from my engine. It only seems to be able to really be heard when I'm idoling when I put it in drive and press the gas and go it dies down slowly and afte a little while it slowly subsides but is still barely audible. What could it be and how can I fix it?

Auto trans?
Noise in front or rear or top or bottom of engine?
Got oil in it and oil pressure?
Might want the check rhe flywheel for cracks and convertor bolts.