Wierd knocking noise

[Atom 8]

My explorer has been making a knocking noise since I got it several months ago. It is an irregular noise, no steady pattern, only at idle and it doesn't do it all the time. I drive it almost every day and hasn't got any worse. Any ideas on what it might be would be appreciated.

 

[rileyrs]

are there any codes?

 

[beatermounty]

Few things to check(if it isnt a rod or lifter) belt tensioner can make some funky noises if its wobbling around, and if one of the cats guts came loose it can make a knocking sound.

 

[Atom 8]

No engine codes, and it only does it at low idle. If I give it just a little bit of gas, hold the idle around 1000 rpm, it goes away. I have had it for about 6 months now and I drive it almost every day. I don't think it's a rod or anything because I can let it sit for 2 or 3 days, go out and start it, and it will not make a sound. Never makes a sound on startup.