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2004 F150 5.4L Misfires


My 2004 F150 5.4L (90,000 miles) misfires when moving from coasting or deceleration to acceleration. The misfire continues until the transmission downshifts and lightens the engine load. This occurs at any speed as long as the auto transmission is in highest gear with OD engaged. No check engine light. My mechanic has scanned twice with no error codes. He has swapped all of the coils with no result. He is mystified and so am I. He has suggested replacing the plugs (which are another issue). Does any one have any suggestion before we embark on the guessing method?

Are you positive it’s a misfire and not just excessive vibration?

Could it be the computer is intentionally not injecting fuel in one or more cylinders and ignoring the resulting misfire?

Does this truck have traction control?

Thank you for responding,
My mechanic assures me that it is a misfire.

I will pass on the second point to my mechanic as it is out of my league.

It doe not have traction control.

He is currently changing the plugs from the Ford issue to “problem solvers” which do not break off as easily. He did state that he is finding a lot of “buildup” and “wear” around the plugs

Thank you again,


Unless it is known for a fact the plugs were recently changed, your mechanic made a mistake by changing all of the coils (ka-ching) without touching the spark plugs.

What is this “buildup” and “wear” of which he speaks?
Now he’s going to install “problem solver” plugs?

Based on the fact the coils were changed and not the plugs, and the use of a few words including “problem solver”, I’m not so sure your mechanic is the right guy to be looking at this vehicle.
I can only assume by the use of the “problem solver” comment that your mechanic is going to throw an overpriced and totally unneeded set of gimmick spark plugs at your truck. Bad.

Faulty plugs can cause coil problems. Since I assume you got hit pretty hard, monetarily speaking, for coil replacement maybe you should should contact the Ford dealer.
Some Fords of this era had the warranty extended on ignition coils to a 100k miles; which means if the coils were acting up it would have been a freebie to you.

How many miles on the plugs?

I would try a fresh set of the original type plugs first.

You could go to a higher octane fuel, even if the octane you usually use is what the manufacturer recommends.
While the spark plugs are out, read their condition by comparing them to these samples:

Maybe the OP meant his mechanic swapped coils to different positions or swapped in a known good coil(s) and put the original(s) back.
That’s what I might do … after I took a look at the plugs.

The plugs have never been changed. The coils were not replaced. They were exchanged one by one and checked each time with no charge to me.

The original plugs have a reputation for separating into two pieces when attempting to remove them. This has happened. They are being replaced with AC-Delco’s which do not have this problem.

My mechanic is a good one that does not charge for what he does not fix. It has been like this for the 20 years or so that I have been dealing with him. He has the city contract for their vehicle maintenance. Needless to say, I trust him.

I’ve had bad experiences with the local dealership and so has FMC since they have forced a change of ownership twice within the past ten years.

Thank you for mentioning that faulty plugs can lead to coils problems. I’ll pass this on. Also for the 100k info.

To date, this issue has not cost me anything except the two days of access to my truck.

Again, Thank you

Thank you for responding.

I’ll keep the octane reference in mind.

I’ve printed your .pdf submittal and will put it to use.

Be well,


Thanks for clarifying what was done.
The problem with the plugs breaking or separating is not due to the fact they’re Ford issue plugs. It’s caused by leaving them in the engine too long.

While it is claimed by a number of car makers, even Ford, that plugs will easily go a 100k miles this should not be allowed to happen.
Even plugs with subtle misfires can damage coils over time and leaving them in place for an extended spell like this can cause them to seize in the cylinder head threads.

Usually when you start moving coils around you also have codes on a specific cylinder and you watch and see if the code follows the coil to its new place. In your case you don’t have any codes so I don’t see the value of moving the coils around.

You express confidence in your mechanic so who am I to complain?

My plugs (all 8) were in the heads for 95% or their rating (95,000 miles) and came out with no trouble. Misfire can masquerade as transmission shudder and visa versa. If you have misfire that you can feel this easily, you should have a stored code for misfire.

Is this a 2V or 3V engine? Has the trans been serviced according to schedule?

Some plugs will come out at a 100k miles and some won’t, but that’s a great point about the transmission service.

Late model Ford vehicles seem to be very quirky about their transmission fluid, which needs to be changed on a regular basis. Symptoms can mimic an igntion miss exactly so maybe the mechanic is barking up the wrong tree.

There is also a Ford factory bulletin about an “incompatible” (not defined as to how) transmission fluid being provided by several suppliers during the time this truck was built. This “incompatible” fluid was supposedly purged out of the suppliers systems some years ago but if this truck has the original fluid and it’s the “incompatible” type maybe the problem is indeed related to the transmission.

Ford made only a few spot checks and relied on the suppliers “policing themselves” in regards to purging the supply system of this fluid so one would hope the suppliers did go that far.

I thank everyone for responding to my original post. I’ve learned a lot thanks to all of you. It appears for now that replacing the plugs has resolved the issue. Only one of the eight separated during the removal process. I did opt for a third party brand to avoid any future plug separation issues. I will definitely keep in mind to replace the plugs before the next 100k.

The transmission fluid is Mobil 1 ATX. I’ve been using synth products on all of my vehicles from date of purchase to date of sale. I don’t know if that really has made any difference. I can state that I was able to get 750k miles out of my 94 Explorer before selling to someone that has reported back that it is still running great at 1,200k.

I do follow the service schedule and am a believer in preventive maintenance.

I admit that I am still a bit perplexed (and so is my mechanic) that no error codes ever showed throughout this process.

Thank you again to all. I now know where to turn if any future issues arise.

Be well everyone.

Until next time,


“still running great at 1,200k”

1,200,000 miles since 1994? That’s ~220 miles a day. Wow!