At 89,000 miles I replaced my plugs with autzone autolites and also replaced my fuel filter. Shortly there after the truck started to shutter and shake while miss firing giving a 0307 code. After checking that plug and replacing it, moving the COPs across the engine from each other the miss firing continued under the 0307 code. The miss firing mostly occurred when I was around 50 MPH, under slight strain with a little acceleration. If I powered through it most of the time it would clear out. Occasionally it was bad enough to where I had to pull over.

I trouble shot this for about a month before it got more consistent and worse. I took it to the shop where they tested the compression on the cylinder and also tested each coil. All check out OK. They recommended I replace all plugs with motorcrafts and the boots on the coils. In the process of doing that I discovered a loose plug in the #2 cylinder. I pulled it out and found that it was scorched and the metal was slightly tweaked at the tip. Not sure how it got loose or how it got burned, but figured that I found the problem. All plugs and boots replaced!

Two days later more miss firing. This time with a 0305 code. Occurs again on a grade at around 50 MPH with slight acceleration. I pulled that plug and the plug in the cylinder where the loose plug was found. Nothing seemed to be wrong. The plugs seemed a little brown where I put anti seize on but that I figured was normal. I then moved coils again. The miss fire continued and the code did not move. There is still a rough idle and occasional humming coming from the engine.

Is the loose burnt plug a separate issue or is there something causing all the miss fires that backed my plug out. I'm lost on my next step to take. Im getting married in two weeks so needless to say spending more and more money on this issue let alone time is making things so stressful. Besides the fact that I think my engine going to blow up on me every time it miss fires bad.

Any help is greatly appreciated! Thank you so much!

 

It could be chafed wiring for the ignition & COP's or injectors. Any other codes? I'd check all the wiring and replace all of the boots whenever changing plugs and use a liberal amount of dielectric grease on the boots. If you are getting a P0191 code or a fuel system related code check those out. P0191 usually is fuel pump driver module.

 

Hey i had a similar problem with my truck after i changed the plugs. It turned out it was some antiseize got down too low on the plugs and was getting on the tip of the plug. I'm thinking it was grounding the plugs out. I removed em and cleaned the antiseize off and just left a reall little bit of it on there and the problem went away. Also when you get the misfire codes say like the P0305 its teling you that its number 5 cyl thats misfiring. Not sure if you knew or not. Hope this helps.

 

I would suggest ditching the autolite plugs all together and putting in Motorcraft plugs. I am not always an OEM type person but when it comes to plugs that seems to be the best way to not have an issue in these trucks. Yes some guys have no problems with other plugs but you read more about the ones who have issues with autolite or champion or whatever type plug it is and most have said problem went away after replacing with motorcraft. Just my 2 cents.

 

Thanks for the replies.

I have replaced all of the Autolite spark plugs with Motorcrafts and thats when I started getting the P0305 coded for that cylinder. It's the only code I'm getting right now. Also, when I put the new plugs in(for the second time, putting in the Autolites was the first) I did replace the boots and put on anti seize. Not sure how I would be able to wipe of the anti seize to make sure its not too low. It looks like on each plug that the nickel anti seize has been turned brown and hardened.

The orginal code when I first replaced my plugs with Autolites was P0307, yet it was cylinder #2 that had the loose burned up plug. I've heard that just because it says one cylinder doesn't necessarily mean its that one with an issue??

Thank you for the continued tips and trouble shooting!

 

Oh I missed that line sorry for giving a suggestion you had already done.

What year is your truck there was an issue with the 04-05's having to do with the injectors so maybe that is what is causing the misfire for you now?

 

Yes, a bad injector can cause spark plug problems. MIght be worth moving the injector to see if the problems moves with it... or simply throw another part or two at it in the form of one new injector on #2. Also, a "liberal" amount of dielectric grease is not recommended, just a dab.

Finally- Motorcraft plugs are made by Autolite using the same materials. I've never figured out how one could be better than another. Like saying a Mercury Grand Marquis is "better" than a Ford Crown Vic. Slightly different packaging but under the skin... same car.

 

I suggest you try another new plug.

I replaced my plugs with champions and then I starting having a mild misfire (did not throw code). After a few months it finally threw a code. A plug was shorting through the ceramic. Replaced that plug and problem was solved.
On wifes van I had a mild misfire. The champions had 40k miles and many were shorting through the ceramic.
I don't know if champions are really bad, or if modern ignition systems are pushing plugs really hard.

 

When you replaced the MCs with the Champs, did you replace the boots? What you describe is a classic symptom of NOT doing so. The reason why, and forgive me if you already did this (I mention this for others), it has to do with the MCs and the Champs have different porcelain profiles. The old MCs are larger in diameter so the old boot doesn't fit tightly and it allows the spark to arc to the plug base. It's best to replace the boots when you do plugs, but it's vital when you change plug brands.

 

I did not initially replace the boots. After a month of mild misfiring (no code) I installed new boots. It did not help. A month later I threw a code so I pulled the plug and found the black spot where the spark was burning through the ceramic. The spot was about halfway along the length of the ceramic. I don't believe the boot covers that much of the ceramic.

In actuality, the champions have a slighlty larger diameter but I agree that it is good idea to change with boots anyway.

On the wifes van with 40kmiles on the champions, the shorting was definitely outside of the boot region.

 

I am starting to go the fuel injector path. I put some Sea Foam in a gas tank two weeks ago with no luck. If I did do the fuel injectors how hard is the operation? That would be a first for me.

It's a 2004.

Thanks for the help.

 

Changing out the injectors isn't too hard just some steps that need to be followed. If you have some mechanical ability you should be able to do it. Since it is a 2004 and the plugs and boots are all changed out then that would be my next step as they were an issue back then.

 

Been all over the map with misfire codes on both my 06 5.4L 3V motors (F150 and an Expedition). Here's what I've learned:
-Use only motorcraft plugs.
-Make sure you are using the correct part number spark plug. The autoparts stores often cross-reference the most recent p/n which might not be the right plug for your year. Using an sp-511 when you should use an sp-507 will cause misfiring.
-A bad injector will foul out a brand new plug. Remove the fuel rail screws, pull up on a single bank, place a clean rag under the row of 4 injectors (while still in the fuel rail), put the ignition in "On" (don't crank) and see if any of those injectors leak.
-Rule out the injectors as quickly as possible. Doing so might save your cats. Also, can you say hydrolock?
-A gummed up throttle body will cause a non-specific misfire code; usually P0305, 07 or 03 in my experience.
-Check the resistance on the COPs and the plugs to help diagnose. It's easy and can quickly exclude the often failing COPs.

 

I have a similar problem. I did use autolite iridium plugs. But when it started missing it was number 7 i did plugs and wires. Its still missing. Not sure witch one. Its a 97 with the 4.6l. Could it b a bad injector

 

please post results when repaired guys!!