Hey all new to this awsome site.Hope to post some pics soon.I have a 05 stx with the 4.6. I have put a k&N filter in along with removing the silencer.My problem is when it sits for a couple of hours or overnight it blows black smoke if you take off right away or rap it a few times.I have had this back to the dealer and they cannot find a problem.I left the truck for a week and they said that they pulled injector rail to watch injectors,checked for latest flash,and even went as far as to check a new 06 on the lot.They told me this was normal however I do not agree.My gas milage is really bad also.I get if I am lucky 11.5 to 12. Any ideas?I know the 5.4 has injector issues...Almost forgot I scanned it at work and I had no codes and all of the monitors have run........Any input would help..........thx guys

 

It depends on how much smoke you are having. Black smoke generally means excess fuel due to incomplete combustion. A little puff isnt unheard off but if it looks like you are driving a hopped-up diesel, then something is wrong.

As far as mileage, welcome to the club. 12 is about average for city driving in an 4.6.

 

I have the same "mods" on my 05 STX 4x4 but no smoke. And yes the fuel mileage (I get 12.5-13 city) is typical of a truck but buying a truck and worrying about fuel mileage is like marrying a fat chick and worrying about the grocery bill.

 

wow, i get 17-18mpg on the 87octane in my 05 stx 4.6L reg cab. granted most of my driving is interstate or backroads, but i have never seen the low teens for my mpg, ever.

 

Try driving in the city, with stoplights every 1/4 mile or less. I get 18mpg on the hwy.

 

have an '06 screw with 4.6....about 10,000 miles...have not noticed any smoke at all!!!!! as for mileage....get around 19-20 on the highway......haven't bothered to check city!!!!

as for your smoke atech765...might change brands of gas!!! might help!!! just my 2cents!!