'01 V8 Sport Model - Bought the car last week with an engine issue. Determined it to be the secondary cam chain tensioner. Had the usual issues of knocking from right side of engine, rough idle, random misfire codes, bank one lean code, etc. Replaced the tensioner yesterday. Since the timing chain did not break, I just left the cam sprocket in the chain where it was while I switched out the tensioner. Started it up and the knocking sound (my dad said it sounded like a washing machine!) was gone, but the engine still idles rough. Runs good at higher RPMs, showed 25 mpg on the freeway, and DID NOT throw any codes! The exhaust still smells too rich. It was doing this before I did the repair. The previous owner, in an attempt to fix the problem, ordered a set of Ebay COPs and replaced all eight. Could the cheap aftermarket COPs cause the rough idle without throwing any misfire codes? He gave me a box with all the original COPs that he removed - should I re-install them? What could be causing the slightly rich smell to the exhuast that wouldn't throw a code? Wouldn't a bad O2 sensor throw a code? So before I tear the engine apart again and re-verify the exhaust cam timing, does anyone have a suggestion for me? Thanks and everybody have a GREAT weekend!