I have the occasional startup engine rattle in my 2007 Cobalt SS with the 2.4L engine, usually on cold starts. It almost sounds like a diesel engine for a couple of seconds, then runs normal after. I've researched this and found that this seems to be a common problem with these engines, and it is usually related to the timing chain tensioner. I was almost convinced that had to be the problem with mine, until I took a few pictures from the back of my engine and found that the head of the tensioner has a bump, just like this one:


Does that mean for sure that I have the latest revision, or were there multiple revisions with this style head? I thought the latest version came out around 2009 or 2010, which would mean there is no way my 2007 would have it unless it was installed later on. I've had the car since it was new, and I don't think the tensioner was ever replaced. Any thoughts?