At an idle my timing belt "clatters". It's hitting the top of the cover, when I remove the cover I can see the belt moving up and down with the engine running. The belt is due to be changed (100k miles) but it looks to be in good shape. Could this be a loose tensioner problem? I've also had a trouble light come on and when read it says the engine has been running too lean. Could this be related to the timing belt? It's a '97 with a 2.0 4 cylinder.
