I have a 2001 f-150 5.4, it has been misfiring while accelerating. I have changed the fuel pressure regulator, and have checked resistance on all the coils all tested okay. While testing the coils I found 2 bad boots and replaced them, but it is still running bad. It is not showing any pending or normal codes. I did replace all the sparkplugs a few months ago and it ran great up till now. I used autolite plugs and did opt for the cheap ones, can anyone help??

 

Based on the 'no code' report, that is the give-away that you have one or more faulty coils. Suprise!.
Meter check will not find the faulty coil hence no code will be set.
Reason is the miss/fault is not a hard fault. If it was, a code would tell you what cylinder it is and case closed.
But what you have is a 'dynamic' fault of a coil with low output not being able to fire it's cylinder reliably every time.
The low output is nearly always shorted turns a meter test cannot pick up.
As to which coil is faulty; you may sub a known good one until you come to the faulty unit.
There are other ways to find the offending coil but require a good scanner and/or a dealer stress test of all the coils to find the one causing the issue.
Good luck.

 

Bluegrass thank a million, I think that is the only other thing to do, also do you think the spark plug brand could have anything to do with it. Should I go for the more expensive brand??

 

Spark plugs?????
You will get a lot of replies that only Motorcraft will work but not really so.
I have run Bosch, Autolite as well as Motorcraft and all work well.
My position is if you want the motor to run first class "most of the time", replace the plugs more often at say about 20k intervals +/- and forget the long term objective of using one plug over the interval..
To do this, use lesser expensive plugs and you will have a motor running better "more of the total time" you own the truck.
My testing experiece has shown that even the hard platnum plugs will degrade after as little as the first 1000 miles let alone 75 or 100,000 miles.
The deal with the hard tip plugs is to allow long running life as a marketing point as well as the cost of labor having a shop do it more often, on these motors.
The Motorcraft plugs also cost a lot more due to the hard metals used for the tips.
Good luck.

 

Once again thanks, you are helping this old shadetree mechanic get through today.

 

Big difference from the old days of carbed motors.
In actuality, the computer does all the same things as the old motors did but with so much more precision and tight control.
Every area is the same from cold start to hot restart and running controls.
With the computer, there is no external ignition except the coils and plugs.
All the timing is computed by the PCM to fire the coils at the correct time, fuel at the correct time and amount, cylinder by cylinder the old motors could not do.
Good luck.

 

My 02 5.4 had an intermittent misfire. I knew it was a coil but had no way if finding which one. Kept driving and it finally threw a code which tells you which one.
Other solution is to buy one new COP and install on #1 cylinder. If it happens again, move to #2 cylinder and so on until problem never comes back.

My bad one actually had a cracked boot and the spring coil going onto the plug was very loose (like it was stretched out).

 

I did the same thing as thomsatl...drove it until it threw a code so I knew which cylinder was missing. Luckily, my neighbor had replaced his F-150's COPs a few months ago. Got one of his known good used ones, and all is well again. Ironically, both of ours were the #3 cylinder.