My 22r developed a strange engine rattling sound the other day and it has me baffled. It seems to be coming from the front of the engine. The sound only happens when the engine is warm and only at low RPM's like from idle to maybe 1500. I thought it could be the timing chain or guides so I pulled the valve cover but everything looked brand new and the chain seemed to have good tension. It was replaced about 50,000 miles ago. Otherwise the truck runs and drives fine. Anyone have any ideas? Thanks for any input!