5.4 V8 runs rough on idle,weak and rough in gear, when cold noice from left main catalytic converter, with warm up fades away.
Got codes for missfire cylinder 7,8. Changed plugs on 7,8. Same.Code came back for 7. Which one is 7 ? driver side or passenger side? I have Ford factory manual on DVD, i've searched it, didn't find how are cylinders numbered.
CODE reader reads only first 3Monitors,M,F,CC, never did read other ones, says error.
I did check vacuum lines,....measured intake vacuum, holds steady, when really hard acceleration, vacuum falls to 0 and you can hear like suction sound from somewhere (only hard acceleration)
Anyway, i'm lost...
Any ideas?
Thank you
Petr

 

could be a coil i have a 2003 with the 5.4 also had my 3 cylinder coil go out and then last week i went mudding and got water and dirt in cylinder 5 just pulled it and cleaned it and it runs fine after that. they should be numbered on your truck i think its on the wire that hooks up to the coil but if in not mistaking it goes

Back
4~8
3~7
2~6
1~5
Front

Hope that helps u could also look it up on google