This is the only code coming up right now. Recent relevant history is that 3 weeks ago I changed out 8 old plugs that were in horrible shape (electrode worn down resulting in overgap) and causing truck to run rough and cough/spit at high rpm. Truck had 67k mi on it.

7 of 8 came out fine, but driver's side/closest to firewall broke on me. Too bad for me I didn't know about the flaws inherent in OEM plugs for the 5.4 3v. Anyway...

I had to drive it 20 miles before getting it to Ford dealer to remove the broken one. During those 20 miles, the truck ran rough as hell and the coil was still attached to the bad plug.

Needless to say, with 8 new plugs in it runs like a different (and better) truck. Almost immediately, this engine light came on and the single code P0430 came up. I'm thinking this error must have something to do with limping on 7 cylinders for 20 miles.

Per www.wellsve.com, this code means:
Only symptom I notice now is a little knocking on startup (hot or cold) and slightly rough idle which settles about 500 rpm. Other than that, it runs fine.


Given the plug situation and having to drive 20 miles on 7 cylinders, what do you guys think is causing this issue?

 

I think you have a damaged cat or downstream O2 sensor. And if it is still running a little rough, re-torque the plugs again, they can work loose. Also, dielectric grease on the boots are a must.

 

I did not use dialectric grease. Where and how much of it do I apply?

Aren't cats usually covered by a 100k warranty specifically?

Is the downstream O2 sensor easy to access? Can you tell if it's bad with a visual inspection? Local auto parts chain quoted me $80 for one and RockAuto.com quotes $48 for Motorcraft.

 

The gas that should have burned in that non firing cylinder could have made it into your cat converter and melted it down some.... Considering the truck ran like crap before the plug change, it could be both cats.... Oddly enough when I had a misfire, my rear most cat was melted down and my front cat was immaculate... This could be from it being a more vertical cat in front while the cat that burned out was completely horizontal and may have gone bad from "pooling gas"...If the cats not rattling then it's probably fine.... If its plugged it will turn bluish or even cherry red after some run time.

I would pull every plug and nickel anti seize the ground shank "but not the electrode" and then dielectric grease the crap out of the COP to plug connection.... If your throwing codes or running rough after that, then it's time to look for the damage caused by the misfire....

 

Makes sense...start with simplest (and cheapest!) solutions first. I didn't do either of those things. I don't remember it being so complicated when I changed the plugs on my '64 Lincoln...or any other car I've owned!

Thanks for the advice, guys.

 

[QUOTE=Especial86;1667706]The gas that should have burned in that non firing cylinder could have made it into your cat converter and melted it down some.... Considering the truck ran like crap before the plug change, it could be both cats.... Oddly enough when I had a misfire, my rear most cat was melted down and my front cat was immaculate... This could be from it being a more vertical cat in front while the cat that burned out was completely horizontal and may have gone bad from "pooling gas"...If the cats not rattling then it's probably fine.... If its plugged it will turn bluish or even cherry red after some run time.

I would pull every plug and nickel anti seize the ground shank "but not the electrode" and then dielectric grease the crap out of the COP to plug connection.... If your throwing codes or running rough after that, then it's time to look for the damage caused by the misfire....[/QUOTE

I would say the same thing regarding the cats. Doesnt make much to melt em down, thats why you never run a vehicle with a misfire

 

Answer: VERY important apparently. Today I took off all of the coils and put a thick bead of dialectric grease on every coil. Also removed all my plugs that I had changed as I mentioned earlier. None broke and were still easy to get out. I put anti-seize on the area directly below the threads and a little on the threads too.

Put everything back in and the truck runs noticeably smoother. The check engine light no longer comes on either. I must not have been getting enough spark to get good combustion without the grease.

Thanks for the advice kanga and Especial86. Who knew a packet of gook @ $1.20 each could make such a difference.

 

Are you kidding me? I didn't think just the dielectric grease would completely fix you're problem. That's awesome! I never used it before on any other vehicles, including a 98 F150, but I put it on every electrical connection now.

 

I agree very important. I changed my plugs and for a few months I would get a slight but fast shake idle at random. I only put a dab of dielectric grease at the end of all my cop's when i first changed them. So I finally took them back off and greased them top to bottom and it's much more smooth and quieter.