My 5.4L 2001 f-150 4x4 puffs blue smoke on start up. It has always done this since new. My dealer could not find a problem while it was still in warranty. The truck has only 14,000 miles on it. I have always used Mobil-1 5w-20w synthetic. I tow exclusively with this truck but it is not my everyday driver. Has anyone else experienced this problem? Could it be my valve seals? Of course it is out of warranty time wise.

 

Sounds like leaking a valve seal symptom to me but I dont know if this is common on the 5.4. I know that older 4.6 engines had this problem.

 

if you use it as little as your mileage shows it very well could be a valve seal but I don't see how it would have done it since new

it is also very common for a defective pcv SYSTEM (not just the valve itself) to cause a little blow by

how much oil does it use between oil changes?

does it do it at every start or just the first of the day?

next time have someone else start it while you put your head near the tail pipe so that you can get a little wiff of the smoke that comes out to make sure it is oil burning and not just condensation

 

Uses no oil between 4000 mile changes, and it only does this on a start-up after it has been sitting a few hours or more. Its not a lot of smoke.

 

My 5.4 has done this also......though not all the time.
I normally notice it only after an overnight sit.
Iv'e come to the conclusion that it is not "oil" smoke but rather a rich start or unburned fuel from injector leakdown while sitting. (I did the smell test as someone else started it).
Just my .02