It is simple to pull the valve cover, but to get a socket on the crankshaft, I have to pull the radiator, the fan and the AC cooler. I can almost see the timing marks, but they are dirty and I can't reach them. Other than that, I don't see how I can get to TDC to check the camshaft mark.
I wondering if the chain stretched enough to jump a tooth, or if the tensioner came loose. I don't know if either one is probable.