2003 5.4 3v lost a cylinder - what would you do?
 

History - Owned since new in 2002. 80k miles. Only mechanical issue was original fuel pump failed last year. Belts, hoses, fluids only (i.e. never touched the plugs for obvious reasons.)

Started running really rough last time I drove it a few weeks ago. As it doesn't get driven much, I put a large can of seafoam in (tank about half full), hoping it was just fuel related (but I have NEVER had an issue with fuel in 17 years.)

Took her out today and CEL was on, when I got home checked and it's reporting missfire on #6.

Knowing the potential issues working on these engines and the fact that it's worth so little now, is it time to move on, or should I try and address it? Could it be as simple as a coil or injector?

You don't have a 3v engine.

You have the reliable 2v engine.

I would do a full tune up. The 2v engine does not break plugs -- they use standard spark plugs.

Go with Motorcraft plugs and gap them correctly.

Yeah, you are worrying for nothing. Just a misfire that should be fixaable with plugs/coil/injector, one or more. The 2 V engines only problem is the spark plugs might blow out if you don't tighten them properly. It's one of the most reliable engines ever built.

Oh thank you! Sorry to be so ignorant.. From what I'd seen and read online over the years, I thought the "triton" was the 3v (hence "tri" in "triton"), and had the 2-part plugs that break off - which is why I never changed them.

So if the code is a misfire on #6, should I start with a single plug and see if it then runs OK, and address the rest if so? Seems like that's the quickest and easiest thing to try. Possibly also swap a coil from one cylinder to another to see if the problem follows the coil?

I know you're all probably rolling your eyes, but at 80k miles, would it seem like plug(s) is likely the cause, or are the coils also suspect?

At 80k and being so old, I wouldn't mess around. Change all the plugs first.

Change all the plugs. Use Motorcraft plugs and torque them to 28 ft/lb. That most likely will fix it. Use a small amount of dielectric grease in the coil boots.

Do NOT use Seafoam in the gas. If you think you need an additive, use only Techron.

Thank you again folks.


I have access to a digital copy of the factory service manual, but is there a "how to" with any tips and tricks, like parts to remove to get at the coils and plugs? Off to search YouTube as well..

Also - which models/years/? had that engine with the "break-away" spark plugs?

2004 to mid 2008 5.4 3 valve.

You may or may not have to lift the fuel rail to get the coils off.

Ignore the factory torque specs, that's not tight enough.

I note on Amazon you can get coil and plug "kits" for $80 - if I'm going to pull the coils to get at the plugs, would you generally recommend just changing the coils anyway?

It wouldn't be a bad idea I suppose to change the coils. But, my 02 is still running well on the original coils at 153,000 miles. I would just swap the coils like you suggested to see if the coil was the problem. I changed my OE plugs at 119,000 miles and it was still running well. The plugs are a pain to change. If you aren't patient, it may be worth the labor charge to get someone else to do it. And, I did have to pull the driver's side fuel rail but that is easy. If you buy new coils only buy Motorcraft, Denso, or Delphi. They are available at rockauto for decent prices. Denso and Delphi supply the auto manufacturers as I understand.

Hmm.. good info.

and if you do change the coils for whatever reason, use Motorcrafts to replace them

Or Denso or Delphi. The cheap coils online are Chinese and are not known for consistent reliability.

With only 80k, yours are probably fine.

eflyguy -- Go back to post #5 and read what I mentioned. -- At 80k, your coils are likely fine.

Make sure you gap the new plugs to specification. They are NOT pre-gapped.

I "rebuilt" my factory coils this past summer. Bought a new spring and boot kit and used vinegar and water and a flat blade screw driver and removed all of the corrosion on the contact point of the Coils. Cleaned well with electronic cleaner and a q tip. ~$25 for the whole boot and spring kit and some of my time. Fixed a ghost misfire I had and runs fantastic. I've used aftermarket before and prefer the factory motorfraft stuff.

I do have a 5.4 3V, but the idea is the same.