I have a 01 F-350 with a 5.4L gas motor and I took it to the local ford dealer for a computer scan, because I've noticed it seems to be missfiring.
So when the guy did the check it showed a misfire in 2 and 5 so I replaced the coil packs on both and I still have a misfire... Ugh so I pulled the plugs and they seem to be fine, what else should I look for?
Is it possible the computer check was wrong and it could possibly be another cylnder misfiring ?

 

Replace the plugs and COP boots if they have not been changed in a while. The spark plugs are best to change about every 50k miles. You can not tell if a plug is good or bad by looking at it most of the time. I have had bad plugs that looked fine but did not work for beans. It is also possible you have contaminated or bad fuel.(possibly water) Run some water remover in the gas to see if that makes a difference. It won't hurt anything. You can get new Motorcraft platinum plugs and boots for a really good price from Rock Auto. Don't buy them from the dealer they will screw you over and charge too much.

 

Ok thanks I'll try that first, I was planning a replacing the plugs and boots this weekend anyway lol
Thanks

 

If that doesn't fix it, it probably will be the actual Coil

 

as a side note make SURE you torque the spark plugs to EXACT specs. you don't want to be helicoiling or replacing heads two months from now when they get spit out.. been there. twice.

 

You may also check the electrical connectors to the coil. Sometimes the little plastic clip could break and does not hold it in. Also, the metal blade in the connector is not making contact so you may need to bend it a little.

 

Does anyone know what to torque the spark plugs too?
Thanks for the help

 

anywhere from 14 ft lbs to 28 ft lbs depending on who you ask. I put anti seize on my plugs and torqued them to 21 (picked the middle) and haven't had a problem in the last 20,000 miles. I highly suggest that you get motorcraft plugs (can get them at autozone) instead of just regular autolite (I know that autolite makes motorcraft). I replaced my factory plugs with autolites and 3000 miles later was replacing them with motorcrafts b/c two went bad. Also if you wanted to replace the coils/boots at the same time there is a seller on ebay who sells said ford surplus cops with the part number scribed off for a really good deal. That's where I got mine from. Best of luck!!!

 

Ok problem still not fixed. Ugh
This is what I've done so far, I replaced all the spark plugs with motorcraft ones
I also have a dummy spark plug to check cop's with, so I checked them and there all
sparking fine. I also replaced all the boots too. And two new cop's for 2 & 5 cyl

Now going back to when I was at the Ford place I had the guy run a scan on my truck, the only thing it showed was #2 & 5 cyl weren't working.
I saw the graph it just showed a downward spike for those two cylinders.

Ok here is the kicker, #5's fuel injector looks newer than the other 7 and the two wires going to that injector are stripped back just enough to check it with a meter.
Now why would that be? Unless someone else was having problems.
I'm not really sure what to check now, and there are still no codes on the truck.

 

I would replace the 2 injectors and see if that helps. Then I would get a compression test as well as a leakdown test and make sure everything Internally is in good shape

 

Ok I'll try new injectors tomorrow and see what happens.
I'm kinda scared to do a compression test because I don't want the problem
to be that bad... Lol Thanks

 

O yeah let me add that on the way to work this morning when i first stated it i smelled gas like it wasn't burning right
Also when you lay into it, it runs like a scalded dog then back fires when you let off of the gas.

 

It sounds like a fuel delivery issue, most auto parts carry the injectors and sell the little o ring kit.

 

I just replaced the two fuel injectors, and i still have the same problem. I also used a 12v test light to test the plug on those two injectors and the light was pulsing.
So now what ? I guess I'll test the compression next.
Any other ideas ?
Thanks for all the help.

 

Ok found the problem, #5 cyl reads 0 psi on the compression test. All other cylinders read 150psi on the money.
Since I just bought the truck used I'm going to try and take it back.
It's just a small used car / truck lot, anyway the guy said he wanted his "Mechanic" to look at it...
I know what I found with these tests, but my question is, Is there some kinda way his "mechanic" can temporally fix this problem to make it look like its fixed?
I don't want the car dealer guy to be like... Well we fixed the problem... And screw me over again.
Thanks for all the help