This is a '94 with the 3.0. I have about 245,000 miles on it. It makes one clear knock sound just as the engine starts. it only does this after sitting overnight. After that one knock sound it will run fine. It won't do it again unless it sits for several hours. This just started a few days ago. I was just wondering if anyone here might have an idea about whats causing this. I realize this is kind of vague, but there's nothing else to tell. It idles well. It accelerates well,(for the 3.slow). It runs normal in every way except for that one knock. It's just that now every time I turn the key, I'm afraid a rod or something is going to come crashing through the block. Any idea's?