Hi. I have a 91 F150 4.9, 300, automatic.
Yesterday, I started hearing a knocking sound which seemed to come from the left side. I couldn't tell exactly where it was coming from or if it sounded more metal-knocking-metal or not, partly because my truck is a little loud. I haven't noticed it when reversing or idling, only in forward acceleration. The knock is constant and increases with acceleration. Oil and transmission fluid levels are fine. There's no extra stuttering, no extra vibration (that's not due to my need for a front end alignment), no vibration or shuddering on the pedals. The problem has worsened since last night. It would begin to stop as soon as I began to brake, but now it takes longer for the knocking to quit. Oh, and, I've had a lot of problems with the fuel system - having to replace and/or clean everything from the tanks up. Don't know if that's related at all. And no smoke to go along with the clunking. Sorry guys, I can change my oil and just about anything on the fuel system from the filter to the pumps, but I am no chick mechanic. Appreciate any help or steering in the right direction.