Hi guys. My new cobalt SS has a rattling or sputtering sound. Kinda like when you use cheap gas or valves knocking. At first i thought the heat shield on the catalytic converter was loose but the dealer told me it was the oil senser that detects the wear. Never heard that one before. I test drove a few other cobalts and made the same noise, especially in low rpm's. I've never owned a supercharged car so i dunno if this is common on them. help please.