My oldest son recently bought a 2000 SD V10. It had 83000 miles on it at the time, this was late May. It ran okay. This past week, it started running really rough, cutting out, missing etc. It got to a point where he had to hold it floored to get 50mph on the highway. Engine light came on, scanned it, P0171 and 174 codes. Lean bank I think it is. We changed plugs, wires, cleaned the MAF, changed the fuel filter and checked for vac leaks. He said it ran like a new truck and he cleared the codes.

He says it still seems to run fine except, twice while he has been driving he said he feels/hears a loud pop almost like a small explosion, feels it under his feet and says he sees what appears to be a flash of fire coming from under the drivers side. Now the CEL is back on and pulls the same codes as before. The CEL had been off for about 4 days before it came back on and the pop/explosion happened 2 days after we had done everything.

Only thing we can find is the first plug (front pass side) when we pull the wire, there is a small amount of coolant on the boot. That may or may not have anything to do with it, just mentioning it because it's odd. Anyway, we are stumped. If anyone has any idea what to look for, or any guidance at all, we would appreciate it. Thanks.

 

What wires???

 

I meant to say cops.

 

The things I've underlined make me think you may have an oxygen sensor and or catalytic converter problem. I am no expert, but a bad 02 sensor may have something to do with the lean bank, which could lead to too much fuel in the cat converter, which may explain the "explosions". I haven't crawled under my truck lately, but I think the cat is where your son is feeling the explosions.

Or I could be all wet.

 

Thought about the cat but it's pretty well behind him as far as feeling it in his feet. Also, after we did all the things I listed, it has been running good. That's where it gets screwy. It runs fine. It runs better than when he bought it and that's pretty good. The only issues are the CEL and codes and the 'explosions' and the flashes. He said once in a while he hears what he describes as air. I suspected a vac leak but at idle and when I drive it, none of this stuff happens. I can't duplicate it.