My engine started knocking, but I can't figure out what the problem is. Have you experienced a similar issue, and have you seen a mechanic? If so, could you recommend someone? I really can't figure out what's wrong.

Honestly, there could be a number of reasons for this, ranging from premature ignition to faulty injectors. You should contact mobile diesel mechanics and have them diagnose the cause of the knocking sound. I had my exhaust system repaired a week ago by Mobile Wrench, so I asked them what kind of repairs they perform. They told me about the possible causes of knocking and rattling in a diesel engine. You can call them, and they will come to you and fix your truck.