I have a 2005 F150 with a 5.4L around 80,000 miles. Every once in a while black smoke with tint of blue shows up on startup. It seams to do it when the truck has set for awhile. I am spooked do to having a engine replaced (at Ford's cost) do to a bad injector. The Engine is about out of its warranty.

 

Sounds rich on startup with some oil burning. POssible leaking injector and bad intake valve seals or rings.

 

X2- you can check the leaking injector if you have a fuel line pressure gauge. Screw the gauge onto the test port, crank the engine. Let it run for a minute and then shut it off. If an injector is leaking, the fuel pressure will drop a steadily. Then the question is to locate which cylinder is the culprit.

 

thanks for the reply's. I will do the test on the fuel rail.

 

smoke sounds like oil slipping down the valve guides while she's sitting. Had an old Honda Prelude that used to do it

 

Try adding about 8oz of STP and see if the cold-start blue smoke ceases. About 4oz of No-Smoke seal conditioner may help as well.

 

I did everything to mine, Sea-foam treatment, New cats, new o2 sensors. etc...

It was a 5 dollar PCV valve.