Thanks for taking the time to read this, here is my problem.

2004 f150 5.4 3v 142,000 miles

plugs done 25,000 ago, fuel pump around the same time as plugs

complete timing job, chains, guids, phasers, sensors, last august (2012)

all filters changed, all normal stuff done, i probably change these more than really needed.

Here is the problem i am getting misfire codes on ramdom cylinders at ramdom times, sometimes months apart from one another, there is no particular order to this at all.

p0300, p0301, p0306 etc for all cylinders at one point or another over the last 10 months

sometimes the codes will be p0351... for what ever cylinder

i cleaned all the connections, made sure all grounds for the computer etc were to bare metal then put some dielectric grease on them for good measure.

I read on a thread that the wiring harness being draped over the metal parts of the ac lines may cause an interuption so i fixed the issue. still missfired about a month later.

all of the freeze frame data is good meaning well within its specs.

this has happened at idle, going 70mph, going 30mph... etc


what do you think?

Replace all COP's?

Computer?

Fuel related?

 

Sorry forgot to say these misfires usually will last around 10-15 seconds.

while it is misfiring the CEL will flash, once it stops misfiring the light stops flashing.

The CEL never stays lit after the misfiring is over...


Also when the codes are stored into the computer they are always "Pending Codes"

and they will clear themselves out if i dont do it within 50-60 mile or so.

again thanks for your help if you have any ideas i have tried everything i know to do up till this point.

next step is to have ford look at it, which i am trying to avoid... most of them are just parts changers not mechanics..

 

When you changed the plugs, did you change the COP boots and use a small amount of dielectric grease? What exact plugs did you use? Have you tried putting Techron in the gas?

 

They are oem plugs motorcraft had them done at the dealer.

I had it all apart when I did the timing job, and yes I cleaned the up the cop's and put some dielectric grease in each one before reinstalling them...

I did not change the boots, the boots were in great shape then unless they have broken down sense...which I guess is possible.

I haven't use the Techron brand specifically however I have used seafoam on a few occasions...

also I had the converters tested and they said they are perfectly fine.

fuel pressure is good
voltage is good
everything in perfect working order other than this weird random misfire...

this is why I have a feeling it is something with the computer or that it may need to be flashed with the latest updates

 

has anyone even had the dealer run a test on the pcm in order to find a misfire issue

 

Gut feeling is COPs or COP boots. Even if they look good, there is a lot of heat in that engine compartment, 150K ish miles is a LOT of exposure to that heat, dirt whatnot...

Not saying it isn't an issue with the computer, however, if it is, it might be a ground issue as the computer itself is typically pretty reliable... Does your truck have rust that could potentially be a part of the cause?

 

Thanks for the reply there is no rust what so ever and I took apart and cleaned all visible grounds in the engine compartment.


Now what I did do this weekend is change the plugs. While in there I cleaned every electrical connection that I had to unplug as well as a few others. Then put some dielectric grease back in all of them. And cleaned the mass air flow again.

I will tell you this truck has never idled as smooth and quite as it is Right now.
Even when I had them changed a few years ago it didn't change the idle. I really was just rolling the dice to see if plugs would help and it feels like it it may have. Or one of the connections i cleaned etc. But as random as the misfire is only time will tell.

Wish me luck.

 

I have the exact same issues, when under load, truck shudders, truck threw codes misfire cylinder 2. I changed plug and COP, then next day threw misfire cylinder 4. WTH!!? Maybe faulty fuel injectors.

 

Did you guys ever check yer FPDM?

https://www.f150online.com/forums/ar...placement.html

BTW - NEVER use Seafoam in these engines - it is crap and does nothing for you (not a single thing in it's MSDS removes carbon deposits) except put yer O2's and cats at risk... useTechron, or if you can't find it fer some reason,Gumout with Regane ...

Just sayin' ...

 

Will look into, truck has never stalled, only shudder under load. Been acting like this for 2 months. Codes won't come back.
Thanks MGDfan

 

Hey i know this is kind of old but have ya'll found out what the issue is. Mine only does it sometimes for a few seconds and only while accelerating at about 2k rpm. I changed the plugs, the COPS looked good and were functioning and it still runs the same.

 

How did you test the cops?