I got the heavier ones just to be on the safe side.

Is the damned thing supposed to sound like a machine gun with the plug out? I started it, it scared the crap outta me, and I shut it right back off before I screwed something up.

While we're here - you think it's unlikely that the sensor is worn on that one cylinder - what else could we be looking at?

When I swapped wires, I used the longest one I could find and ran it way out around the others to be sure it wasn't close to any.

 

I went ahead and let 'er run for a minute while I checked spark - my next door neighbor came out thinking someone was shooting at the house!

Anyway... there's definitely spark.

I guess after dark I'll start it up and see if I can spot any spark jumping to ground anywhere. (wouldn't that be nice...)

Could it be a plugged or dead fuel injector on that cylinder? Or do you think it's the PIP sensor? ICM?

Or maybe something else?

 

It's dark outside, and with it running I can't see a spark jumping anywhere.

Seems odd that it has spark when it's out of the motor, but not firing with it in. Does that sound like a fuel injector? Stuck open or closed?

 

Sorry, I had to go to work earlier. The only reason I was home at that time was to meet an insurance adjuster. You have found that you have spark, so you aren't getting fuel to that cylinder. The injector may be clogged or bad, or it may not be getting power or ground. Check the wiring first. The injector gets power always with the key on, and is fired by the computer by adding ground. So check for power then make sure it's getting the ground signal.

 

It's #3 - on a 5.0 that's about a mile up under the intake... how the hell am I supposed to get to it with probes?

 

There just can't be anything easy to fix on your truck, can there? You can trace the wires back to a more convenient location to test them, but if the break is under the manifold that won't help. I also don't understand how the computer distinguishes between the cylinders, because one ground wire fires four cylinders and one fires the other four. What you should do is disable the fuel system, remove the upper intake and then test it. Try to leave as much plugged in as possible since you will be cranking the engine, and run the fuel lines out of gas before taking anything apart so the engine doesn't try to start with everything taken apart. Since you will need to take all this apart anyway to change the injector or repair the wiring, it won't be a big deal. But check the wiring where you can get to it in case it's bad there and you don't have to take everything apart.

 

The way the wiring routs, the wires rout all the way around the fuel rail, and branch off at each injector. If it's a bad wire, it's gotta be in the 4-6 inch pigtail running to that one injector (I would think).

You're thinking that it's not getting fuel, right? If it was stuck open things would be a bit different? I kinda need to drive the thing to work and back (10 frustrating miles each way) until I fix it, unless it's gonna load the cylinder with gas and blow the head off.

Seems like it would have been blowing gas out the spark plug hole when I had it out if that was the case, though. And I looked - nothing was spraying out except for air and noise.

 

Borrow a timing light and clamp the p/u lead over the #3. You can check your timing too. Switch plugs to rule out a cracked insulator of the plug & make sure there isn't alot of muck at the opening for the plug that would allow current bleed off path to the block. If your slightly off center when torquing in the plug the insulators can crack easily, though cracking the #3 coincidentally isn't a great bet.

 

I'm actually one step ahead of you on that deal... I swapped plugs with no change, even swapped wires with no change. Checked around the plug opening and it was quite clean. Watched it run in the dark to be sure no spark was jumping from the wire.

Gonna have to get a timing light though!

 

I don't think the injector is stuck open, and if it was you would get a "Oxygen sensor indicates rich" code. Here's what you do know. One wire supplies positive to all injectors and it splits into eight, so you are getting power but you don't know if it's reaching #3. One ground supplies ground to four injectors, and 3 of them are working, so you are getting the ground signal but you don't know if it's reaching #3. Your problem lies under the upper intake whether it's a bad wire or bad injector. I think it's more likely the injector, but I would test the wires just to make sure money isn't wasted.