>Auto Repair Mystery Solved
I tried many things to fix it including changing spark plugs, trying ultra-premium gasoline (with octane boosters), changing the O2 sensor and fiddling with the timing.
I suspected that the anti-knock sensor was bad because of all the knocking and pinging. Another symptom was that there was no water circulation through the heater core. I was told this was either because the heater was plugged or the valve wasn’t working.
Apparently (I hope) the problem was that the water pump impeller had become disconnected from the shaft. You can see how it has rubbed on the housing. It wouldn’t turn enough to force the water to move.
I have one of those ‘mechanic’s stethescopes’ that allows you to listen to engines. I was able to hear an occasional metallic grinding noise from the water pump.
When I removed the pump I found the problem.
I sure hope this fixes it because it’s a pretty nice truck considering it’s 18 years old. I hardly drove it so it has less than 85 thousand miles on it. That’s less than 5000 miles per year! Heck, I put that many miles on my Shoes.