I have a 2004 ion2 coupe with the 2.2L Ecoteck. Just this morning it started a knocking noise, best I can tell, in the front. It only does it between 15 and 25 MPH. And only when my foot is off the gas. Goes away as soon as I press on the gas or when I slow down below 15 MPH any ideas? Thanks

 

First check for a loose wheel! Then I would run it in the air. Jacked up, rear wheels chocked, very secure or take it to a shop. May be an axle or a warped rotor making the caliper thump.

 

These cars seem prone to sway bar bushing end link failure.
Check thoise.

 

Check the upper strut mounts, the sway bar bushings, the end links... An oily coating on the strut body means it's broken and leaking its fluid...