5.4 Ford engine codes

[Hiking Doug]

New to site, thanks Arctic Traveler for introducing me to this forum.
My 2002 Ford Econoline, 5.4 engine is throwing two codes on startup, any help would be appreciated
PO 316 - Engine misfire on startup
OO 304 #4 misfire
I replaced all 8 plug ‘coils’.
Note: the frequency is increasing and presently in Alaska.
Doug

[carringb]

When's the last spark plug change? Have you pulled the #4 plug to check its condition?

If the plugs are current, and #4 plug looks ok, you probably should run a relative compression test (dealer scan tool or equivalent).

Also, check the not-so-obvious... Did you actually plug the #4 coil back it after swapping them? Easy mistake to make. Ask me how I know...

One more thing... when was the fuel filter last changed. When it plugs, you misfire one cylinder first (end of the fuel rail) before it finally gets bad enough for others to drop out.

[arctictraveller]

How about that Doug? Took what, little over an hour to get an answer, and it came from one of the best. Welcome to the forum, there's plenty of good folks around here. I've got tools and spares if you want to give it a try before you head South,but I'll probably head to Palmer early afternoon if you don't. You can call me.

[Hiking Doug]

Thanks for replies. Checked plug, all secure. Heading south due to smoke, code has not returned, yet. Only appears on startup, first 1,000 revs. Will do work in Bellingham.
ArcticTraveler, safe journey and again thanks for introducing me to this site.
Doug

[86Scotty]

You’re in Alaska. How is the weather? Does it happen after rain?

[Hiking Doug]

Weather has not seem to affect it. Still in Yukon Territory, weather dry, warm and a lot of smoke.

[PetiteautoRv]

Originally Posted by Hiking Doug

Thanks for replies. Checked plug, all secure. Heading south due to smoke, code has not returned, yet. Only appears on startup, first 1,000 revs. Will do work in Bellingham.
ArcticTraveler, safe journey and again thanks for introducing me to this site.
Doug

We’ve had an issue similar to this on various units (although rare).
- How long does it need to be sitting before starting it up to cause the issue to occur?
- does the van have to have been running up to a certain temperature before shutting it off and turning it back on?

One theory: if an engine has a slight head gasket problem, this may cause slow seepage of antifreez into a cylinder. This happens usually after the engine ran enough to build some pressure in the cooling system. Once the engine is shut off (usually for some time), the combination of a faulty head gasket and relatively high cooling system pressure may allow antifreeze to enter the cylinder fouling out the spark plug. A misfire would occur upon next startup and clear up within seconds after the accumulated antifreeze burns off.

We have tested this using a bore scope and cooling system presurizer. We would remove the spark plug of the effected cylinder, camera scope the cylinder while pressurizing the cooling system. Careful inspection of the cylinder walls would reveal the antifreeze intrusion if present.

Hope this helps!

[Hiking Doug]

Usually the van has sat overnight making your theory something I need to checkout.
I appreciate your input and will now log when it occurs.
To all who have responded I send my thanks.
Doug