not showing a code

[gdubya]

My sho was and still is missfiring after replacing back 4 plugs and packs, front packs are good, computer not showing any misfires? any help out there? Also brakes not gettig a vaccum

 

[jmpSHO2nd]

Sometimes it takes a little while for a misfire to show up on a Ford.

 

[gdubya]

how long

how long? I let it run for 30 min. also the vaccum on the brake assist isnt working can that make it run poorly?

 

[kevinspann]

Yes it can. Is the vacuum line connected to the intake manifold?

 

[gdubya]

yes it is