This may help a few of you out that are having problems with noise on cold mornings but are not sure if it is "piston slap" or not... When i had 5,000 miles on my 99 F150 5.4ltr, one cold morning i started hearing a tapping/popping/knocking??? noise from my motor. It sounded like it was comming from inside the engine and lasted until i was down the street a couple of blocks...then it went away until the next morning. I let it go for a few days of hearing this noise...it warmed up about 15 degrees and the noise stopped for about a week. When the temp. dropped the noise came back. I brought it by my ford dealer...the first dealer said:"UUUHHH i think its the air conditioner"...knowing that it wasn't the A/C...i brought it to another dealer and spoke to a mechanic this time. He sent me home and told me to try a couple of things for him...he asked me to spray my main belt with a little water in the morning IF it was knocking...(by this point it was quite noticable, i would actually look around to see if anyone was looking..lol) Sure enough, i shot it with a little water...and the noise stopped....WOW...for the next three days i shot it with a little water...and it worked... I called the mech. back and he told me to bring it in, that he has had to change quite a few belts and a couple of pulleys to correct a popping-nocking noise that has been occuring only during cold weather.... He checked the alignment of my pulleys and replaced my main belt. No problems since.
Some of you out there may have the old "Piston-slap" or may be using the wrong filter(also causes a litle ticking), but if all else fails...try a shot of water...strange enough...it worked...

I Hope this could be of some help....

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99 F-150 XLT ExtCab 2WD
Gold/Tan, Hitch, Factory
5.4(mfg date 5/99)

[This message has been edited by ksdoxey (edited 08-24-2000).]