so now that I got the brakes figured out thanks to you guys figured id come back with my new issue. trucks throwing codes for cylinder 3 and 8 misfire. I pulled the plugs and both were covered in oil and cylinder 8s electrode was literally gone. so I replaced the plugs and within 5 miles it was missing again. so I replaced all plugs, all wires and coil packs. cylinder 8 plug had fouled out. need some advice here. its a 4.6l 99. I have a mild exhaust leak where the manifold connects to the downpipe. but not bad enough I feel it should matter. it runs rough until about 3k rpm and then it kinda straightens out.

 

Do you have a check engine light come on? Might be bad 02 sensors that are causing the problem.

 

I do have a cel. just for the misfire codes for 3 and 8 though, is there any way to test the o2 sensors? or could I try unplugging them?

 

If you have oil on the #8 plug, something else could be wrong. If #8 had/has been misfiring for a long time, you have been spitting fuel down that side cat.

You need a competent mechanic to inspect the plugs. There could be multiple reasons for it being wet. How long did you drive it before changing the plugs when it first threw the codes?

 

Just for clarification, were the electrodes "covered in oil"? Or were the plugs submerged in oil in the sparkplug wells?

 

Just the threads, and the electrode. The well was not submerged or full. And I have no clue how long it's been missing, I bought it from a friend. I changed the plugs as soon as I got it the 10 miles home, I'm going to punch the cats out this weekend and see if that helps. I know they're getting way hotter than they should.

 

What will punching out the cats accomplish? So all the cylinders are OK now except #8 that is fouling? Is the electrode actually soaked in oil?

 

Just on the off chance the cats are clogged, and cylinder 3 still has a random miss but not bad 8 consistently fouls plugs they usually come out with oil cooked onto them, when I first changed them and I pulled 8 the electrode or where it should be was covered in oil.

 

If the cats are bad you will almost always get a code for that .The rear o2 sensors on both sides monitor that.....that is all they do. It will be a "below threshold" code. Be sure you scrolled thru all the codes when you checked them and see if that is in there. Might want to run a compression test on #8.

 

Yea, that's the plan on doing a compression test on 8, and it threw one single code that was something along the lines of below threshold I don't remember exactly what it was. Thanks alot for the input/advice. I'll let you know what I figure out

 

I was thinking the chance of a bad or cupped valve on cylinder 8.

 

Good luck....let us know what you find.

 

O.K. Hill, before you go trashing your cats, lets walk through this:

1. Wet spark plugs on EACH bank: 3rd back on driver side (#3) and 4th back on passenger side (#8).
2. Changed plugs and truck starts missing again very quickly (5 Miles).
3. #8 plug still has wet electrode area and threads.
4. There IS a code for something below threshold .

O.K., I'm far, far from knowing much about the 4.6L (I struggle enough with the 5.4L) but for the group to come close to helping you, we need ALL the codes that you have received. I know this may be a pain, but there are folks who come here with a WEALTH of knowledge. For them to help, they need to know what codes you are receiving. If you can, don't just throw parts at it, or make stuff inoperable.

If anything, the wet plug COULD indicate 1. Bad valve guide seals, 2. STILL not firing coil and wire, 3. Stuck fuel injector on #8, 4. Bad intake valve, or possibly more. A non firing coil and wire CAN cause the build up you saw when you first pulled #8. You very well could have a destroyed cat on that bank if enough raw fuel has passed through. But if you trash it, you will have a constant CEL due to the rear O2 sensors reading high.

First thing I would do is swap the wires for #8 and say #4. Same length, go drive and see what happens.

 

I was already thinking valve/s I'm gonna do a compression test as soon as it's warmer than 10* haha, and I just ordered in 2 new coil packs, wires and plugs again from rock auto this time. And I'll see what that does too. Thanks for the advice

 

No, #3 is third back on the passenger side.
No, #8 is fourth back on driver's side.