I have a 1999 f150 with a misfire on cylinder 6. I have already checked fuel pressure, vacuum lines, has new injector, new plugs, new coils, wires were tested and are good, any advice on what it could be?

 

Check compression.

 

Sorry forgot to mention i already checked compression and it was good

 

So did you have the misfire before all the changes or after ?

 

It was before

 

What brand did you have for parts before and after ?

 

What motor?
How much compression?
What was the number and did you possibly turn it over too many times building a false compression reading?
The intake manifold gasket leaks?
Something loose on the intake manifold near the # 6 port?

 

It has all motocraft parts for replacement, it is a 4.6, I do not remember what the compression actually was it has been a week since I tested it and it is possible I cranked it too long, there is nothing loose on the intake, how would I check for an intake manifold gasket leak?

 

How long since you made the changes? These trucks need to go through some drive cycles before the computer smooths out the engine with the new parts. Had that happen to me. Changed out all the plugs and wires after a misfire code and it took like 3 drive cycles before the engine ran smooth again.

 

I have only drove it once for like 3 minutes since it still had the misfire. Been a few days since I put the parts on. What are you calling a driving cycle? Like drive it for 10-15 minutes at a time?

 

https://www.checkengine.me/drive-cycle-wiki