my 08 F 150 5.4L V8 has almost 90K miles.....did my plugs around 8K ago.....

Is there any general rule of thumb on replacing the coil over plugs ?

thanks

 

When it develops a miss with known good plugs in it.

 

And, if you put in new plugs when it starts, check the new plugs. Doesn't happen often but once in a great while. I have the brown boots and replaced one after 150,000 miles on a 2008. If you suspect a coil pack, clear the ODBC codes and move the coil pack to another cylinder. If the problem moves with the coil pack to the new cylinder then replace the coil pack...good luck.

 

thanks !