3.0L Cylinder #5 Misfire

[G8orFord]

Is number 5 plug wet after running it a little while? If it's not firing and the plug is wet, then you can be reasonably assured that it's getting fuel. If it's dry, it's either firing or not getting fuel. Any possibility of a plugged intake port? Maybe an errant shop towel or something? Fact is, if the other cylinders are firing and you have compression and ignition, the only thing missing is fuel. That said, I have seen coils that would spark outside of the cylinder but not produce enough spark under compression to ignite the mixture. I'm not one to throw parts at a problem, but for the price of a coil, it might be worth a shot.

 

[Sharky146]

Is number 5 plug wet after running it a little while? If it's not firing and the plug is wet, then you can be reasonably assured that it's getting fuel. If it's dry, it's either firing or not getting fuel. Any possibility of a plugged intake port? Maybe an errant shop towel or something? Fact is, if the other cylinders are firing and you have compression and ignition, the only thing missing is fuel. That said, I have seen coils that would spark outside of the cylinder but not produce enough spark under compression to ignite the mixture. I'm not one to throw parts at a problem, but for the price of a coil, it might be worth a shot.

I guess it’s wet, but it’s not dripping wet. This is a close up pic taken right after removing the plug from #

 

[Sharky146]

Is number 5 plug wet after running it a little while? If it's not firing and the plug is wet, then you can be reasonably assured that it's getting fuel. If it's dry, it's either firing or not getting fuel. Any possibility of a plugged intake port? Maybe an errant shop towel or something? Fact is, if the other cylinders are firing and you have compression and ignition, the only thing missing is fuel. That said, I have seen coils that would spark outside of the cylinder but not produce enough spark under compression to ignite the mixture. I'm not one to throw parts at a problem, but for the price of a coil, it might be worth a shot.

Here’s a pic of the #1 plug. Looks a lot better to me.

 

[8thTon]

Electricity is a gaping hole in my car repair game. It seems to be mostly black magic to me. Haha!

But seriously, I’m undereducated in the science behind how the truck’s 12v system makes everything work. Are you saying that the coil pack could be bad? Or that the #5 spark plug is somehow shorted?

Replacing the coil pack would be simple. However, #5 is shorted, what’s the fix for that? New head?? The plug grounds to the block (through the head) as you mentioned, right?

The coil pack can fail of course, but since you swapped outputs at the coil and the problem stayed with the cylinder it's hard to see how that could be it. Somehow having a short at the plug would do it, but how could that happen with two different plugs - unless it's oil fouled or something? I gotta say, that #5 plug is dirty and looks like it has been firing something! If it was a new plug and never fired it should be wet and a little gross, but not dirty like that.

So I guess I have been thinking it was not firing at all, but your title does say misfire. Then it has compression, fuel, air and spark but it's burning poorly? Oil in the combustion chamber fouling the plug?

 

[sheep herder]

Oil in the combustion chamber fouling the plug?

Plug looks oily to me. Could have a little fuel too but it doesn't really look like it hasn't been firing.

 

[Sharky146]

Plug looks oily to me. Could have a little fuel too but it doesn't really look like it hasn't been firing.

Guys, you might be onto something regarding oil in the combustion chamber. This engine came from a wrecked ranger that had flipped over. When I pulled the plugs out of it, oil poured out of at least one spark plug hole. I can’t remember if it was #5 though. I drained it the best I could, and thought that whatever oil was left would just burn off when I started the truck. Perhaps that’s not how it works?

 

[mikkelstuff]

Will be interested to know if you find a solution. I have a very similar problem with the number 4 cylinder in my 2002 3.0L (140,000 miles). The only real difference is that I can never feel the miss. Mine is most erratic and may go months before it turns up again.

Oh yes, I have tried all the procedures you mention. I even replaced the number 4 cylinder injector as a can of BG-44K fuel cleaner would always clear the problem for a couple of tanks of gas.

So I am wondering if there is a better coil pack made for this engine than a Motorcraft?

 

[Dirtman]

Your using NGK plugs in a ford... there's your problem right there.

 

[Sharky146]

Your using NGK plugs in a ford... there's your problem right there.

I just bought some new motorcraft plugs and a new BWD coil pack. Not sure the plugs make much difference in this situation, but it can’t hurt to minimize the variables I suppose. I’ll try to get it put back together today and I’ll be sure to post the results.

 

[Sharky146]

Ok, I think I found the problem, as unlikely as it may be. So, when I put the engine back together, I decided to move a known-good injector into the #5 cylinder. As you probably remember, I bought a brand new injector for #5 over the weekend. Well, I moved that new injector to #6 and reassembled the motor. It started right up and now #6 is misfiring. I did all the normal misfire troubleshooting (swapped wires, plugs, etc.) but #6 is still misfiring.

It seems crazy to me, but I think the original #5 injector was bad and I replaced it with a brand new one, which was also bad. It was a $60 BWD injector. I just bought a motorcraft injector from Rock Auto, which should be here on Thursday. Fingers crossed that it does the trick!

 

[8thTon]

Ok, I think I found the problem, as unlikely as it may be. So, when I put the engine back together, I decided to move a known-good injector into the #5 cylinder. As you probably remember, I bought a brand new injector for #5 over the weekend. Well, I moved that new injector to #6 and reassembled the motor. It started right up and now #6 is misfiring. I did all the normal misfire troubleshooting (swapped wires, plugs, etc.) but #6 is still misfiring.

It seems crazy to me, but I think the original #5 injector was bad and I replaced it with a brand new one, which was also bad. It was a $60 BWD injector. I just bought a motorcraft injector from Rock Auto, which should be here on Thursday. Fingers crossed that it does the trick!

Not much makes troubleshooting difficult like swapping in a new bad part, but I've had it happen. Good luck!

 

[Dirtman]

A wise man once said "new just means untested".

 

[Sharky146]

I replaced the bad injector and now she’s running great!

Thanks for all the help on this issue. The Ranger Station has been an excellent source of wisdom and knowledge, which has made my quarantine project possible. Thanks again!

 

[RangerVet]

I was unable to get a TPI Chevy to fire a few years back. I purchased a Noid Light kit from Autozone and tested each injector. After using it I returned it to the store and they gave me most of the purchase price back. Neat little outfit. The Noid light lets you know if the injector is actually firing.
Have you tried a bore scope to see if the intake valve is actually opening? You can rent that too.

 

[Snoranger]

A wise man once said "new just means untested".

It wasn’t a wise man... I said that.