I have a 02 f150 4.6 I replaced the spark plugs. now it it runs but rough so I replaced all the coils. still the same.I have checked the fuses there all good anyone have any ideas.

 

Check for vacuum leak. Especially the elbow at back if engine. Also, clean the IAC.

 

welcome to the site!

Are you getting a check engine light?
what brand plugs?
what brand COPs?
Did you gap them right?

 

Which plugs did you use? Which coils?

Has to be the plugs, if it just started happening after they were changed. I've seen that happen before when switching to Autolight brand.

Unless you not getting a good connection at one of the coils. Or something wrong or forgotten. Has the CEL blinked at yuh?

 

Check to make sure you didn't fold or jam a plug boot between the spark plug and cylinder wall. That's easy to do, specially in #4 or 8's plug chamber.

 

had bosch plugs first thought they might be bad so changed them to motorcraft gap at .054
araparts coils cheaper but there copper.no codes and cannot find vauum leak

 

just found the problem vacuum leak at back of engine
thanks for the help

 

Ahh the infamous pcv elbow ha.

Glad you could find it!

 

Good Job!

 

You're welcome!

 

...Nailed it!