I have 2006 f-150 5.4. check engine light came on after noticeable miss. Code said #1 and #8 misfire, and multi-misfire. Changed coil packs and plugs on both cylinders, still has terrible miss but no check engine light. Any suggestions?

 

How many miles are on this vehicle ?

 

130,000

 

130,000

 

More than once bad plugs and coils have taken a good tech for a ride because he assumed they were either replaced a short while ago or "seemed" to look OK.
Those 5.4s don't like other than Motorcraft plugs and the coils have been quite troublesome. If the coils have never been changed I would consider replacing them because if they produce a good voltage spike in the system they can destroy the PCM and it's cheaper to replace the coils than the PCM. I know OEM parts sometimes cost more than some aftermarket ones , but they do solve the problem. Also check the plugs where they connect to the PCM because moisture intrusion there can produce some results similar to what you are seeing.

 

plugs are going bad. just had mine changed a few months back. it was doing the same thing