Sometime I have trouble getting the truck to start. This began 2 weeks ago. Checked the battery, altenator, and starter. All are good. When it does this it won't turn over just ticks, then hesitates to roll over and after fighting it a bit it finally starts. What would cause this? Also today there is suddenly a loud knocking noise coming from the engine. I hear it loudly from both the driver and passenger sides. Maybe a month ago we changed the spark plugs and wire. We bought something new. Could this have been the cause?