I have a 2001 supercrew with 5.4 it has 100,000 miles on the clock and it had a tune up at 90,000 miles and new Accel cop's at 95,000 due to a bad coil! I was driving it today and it sounded like a rock hit the windshield then the truck started to miss then the engine light came on! I went back home and put my code reader on it shows #6 misfires I pulled the plug and cop they look fine? At first I thought the plug might have blown out but it was as tight as I put it in no problem! My question is how to test the Cop with a meter ??? Any other suggestions please help!!

 

I just replaced the boots on mine and while doing so, checked my coils. Primary resistance is checked between the top tangs and should be .55 ohms. Secondary resistance is 5.500 ohms and checked between the top and bottom of the coil. My truck has 119K on it and they all checked out.

 

I get 6.5 ohms from the top to the bottom of the coil and it varies between the two tangs it reads 00.0- 00.8 it doesn't stay consistant !

 

checked a few more times I get .6 ohms on the top two tangs and I get 6.54 from top to bottom! I checked one on the # 4 and get .6 ohms on the top and 6.43 on the top to bottom! I am guessing they are both OK so if everything checks out on # 6 why am I getting a missfire code on #6??? What else might be wrong??

 

Have you tried swapping the #6 cop with say #1 and see if that changes things? If it still shows you have a misfire at #6 you know you have something else going on.

Is the engine still running rough? Might be time for a compression test and see what the status of cylinder #6 is.

 

Yes it still is running rough I did check the spark plug and coil on #6 they both seem good is it possible the computer is reading the wrong cylinder!!! I don't have a compression tester where can I get a cheap one?

 

Switch the cops and see what it does. That noise you heard bothers me.

 

Yea me too It sounded like a big rock hit the hood! But my oil pressure and temp were fine and no knock in the engine just a miss? I am hopping it was just a plug or coil and not a valve !!!

 

Most any auto parts store will have a cheap one.I bought mine from a local "Discount hardware" store Harbor Freight.Its definately not designed to be used daily,but has worked well for me over the years.
Also,the "noise" you heard concerns me as well,IF I have my guess,the compression check is going to reveal the "oh S++t" scenerio...hopefully im wrong.....

 

I have to work 12-13hr days until Thursday so I won't be able to pick up a compression tester until then. I have been working on pulling the coil packs off and checking each spark plug to make sure none of them blew out!

 

Well I got a compression tester and all 8 check out good so nothing major internally! I then started the truck and pulled each injector plug one by one and they all are working like they should! Then I did the same with the coils and all of them made it idle rougher than it was so I am very confused??? I cleared the codes then went for a drive it is still missing and bucking but as I accelerated it was hit and miss it would kick in and have good power then go back to missing? I got back home then checked the codes again still miss firing on # 6 so I pulled the coil and put it in #1 then cleared the codes again! I took it for another drive still missing then checked the codes when I got back and it came up as # 1 missing and multiple miss firing! I think that maybe the coil is only getting half the voltage or something because it changes the idle when I unplug the coil at idle! I hope that is the problem anyone else ever have this happen?

 

Change out that coil, it should solve your problems.

 

yes, that coil is breaking down and only firing part time. checks o.k at idle, and sometimes when under load, but misfires other times. you found it when you switch the COP to the other cylinder-- thats it.

 

I ordered a new coil right when it showed the miss fire I just got the coil this morning and put it in now it purrs like a kitten! I also treated it to new set of headers since my exhaust manifold gasket blew out! I figured as long as I had to take it all apart I might as well install a new toy and it sounds great not to mention more power and hopefully mpg's!!

 

I forgot to say thanks to everyone for there reply's !!