Engine Knocking, any Ideas?
My 92 F150 4x4 5L auto runs pretty well. I went through some work with EGR codes and replaced some sensors, fixed some vacuum leaks etc. I am still left with one nagging problem.
When towing or hauling a heavy load, the truck has a bad engine knock, which I believe to be the valves rattling. This occurrs, usually on uphill grades. When the truck is empty, there is an occasional ping or two, but nothing major. Last week I pulled a trailer load of hay and the knock was really bad on some steep hills. As the speed went down the noise was worse and it began to overheat. I use it as a work/farm truck and only drive it once or twice a week(not my daily ride). So, it is not something I deal with every day. I have noticed that the truck seems to have a slight miss when idling, but nothing when accelerating or driving. The only other symptom that might be related is that the truck is slow to fire. When I start it, it grinds a while before it fires up. This is better if I make sure to let the fuel pump stop running before I turn it over. It seems to do better if I turn the key off and then let the pump run a second time.
I have tried, premium gas, oil additives, adjusting the timing and no significant change. The guy who had the truck before me did a lot to it, new wires, egr and some sensors. I don't want to start throwing parts at it without an idea of where I am headed. My first thought was plugs, wires, cap and rotor, and maybe knock sensor and coil. It has super stock wires that appear to be 2-3yrs old. Those parts add up quickly.
Any ideas on where to start? I want to start with the least expensive, and most likely problems first.