1997 Chevy Malibu Knocking

Your co-worker is probably wrong. If your valve comes into contact with your piston, your engine will self destruct almost immediately and you'll hear a lot more than just a "Knocking".

If your check engine light is coming on, then start by having your computer scanned.

Your knock could be ignition timing/fuel related. It could also be mechanical, such as your oil level is low and starving your valve train/lifters of lubricant or your pistons are excessively worn and slapping against the cylinders.

There are several possible causes of a knocking sound, but they can only be properly diagnosed by a mechanic with the proper tools.