Hi guys. I have not posted any thing since 2007. No problems till now. Have 99 F-150 5.4L. Pulling boat from Fla on weekend. engine started hesitating. Called my local Ford dealer, who was pulling boat ahead of me on I95. He said COP most likely causing problem. Suggested change in RPM"s. I dropped out of OD and it smoothed out. Made it home. Today stopped by auto store and had codes checked. No codes. ? how can you determine which COP is bad with no code?? Problem comes and goes. Thanks to all.

 

Good for your dealer friend, he got it right.
The coils can intemittantly develope shorted turns and reduced the coil output voltage.
In OD at light throttle the A/F ratio goes quite high over 20 to 1.
At this ratio, it take more coil voltage to fire the lean mix. If it can't, you feel a miss or hesitation on that cylinder.
Since it not a "Hard" fault, no code will be set because it is not in full time.
As soon as you call for extra power, the A/F ratio goes richer and is much easier to fire hance no miss and any stored memory of the miss on the cylinder is erased. ( the PCM backs out of the routine) with increase in throttle/rpm.
Only two ways to address this.
Dealer stress test to pick out the coil or replace one at a time by moving a good one into each cylinder until you find the the one that clears the problem.
Be awhere that mass change 'could' introduce another bad coil and cause confusion so take that into acount in the final analysis..
I would sugesst using an OEM coil not any aftermarket, for longevity.
.
The reason this happens under certain conditions is the fuel is cut back, EGR is opened making the mix very lean by design as well the ignition timing is advanced because the lean mix must be fired with more lead time to have the max. cylinder pressure occurr at the same point relitive to crank /pistion position after top dead center.
The whole process normally is not felt by the driver if all the actions are proper in operation.
So you can see that there is a lot of things going on you don't know about until one or more parts of the whole system go in trouble.
Good luck, you got the whole explanation.

 

Additional comment about coil failures.
Coils live at the top of the motor and in the open where a lot of heat is soaked up from the motor, exhaust manifolds and radiator.
In summer's hot temps the coils get soaked with heat without benefit of airflow cooling when the motor is shut off after a drive cycle and anytime the hot motor is shut off.
This is the time that coils begin to suffer failure that once it happens does not go away.

 

For the price of one OEM cop from the dealer, you can buy a whole set of 8 from Global or Uneek on Ebay. Search for "dg508". Change them all and keep the old ones for spares.

 

Bluegrass,
until I read what you wrote explaining all of this I was stumped, now it makes sense. I have a 2003 F150 supercrew 4X4, 5.4L it was running decent at lower RPM, but once it started to warm up and I eased up on the gas peddle, say around 1500-2000, it would buck, miss, and stumble, but once I pressed down hard on the gas it would smooth right out. It did throw a code every now and then, 171 and 174, lean bank one and bank two. I replaced the Mass Air Flow Sensor being told by Autozone that was the problem, and it still acted the same. I took it back to Autozone, and they exchanged it, but I still had the problem or the buck, miss, and stumble. It never showed a COP until it completely went out, then it showed #2 COP was bad. I replaced it and the truck is running fine, with just a bare hint of a miss. I have now ordered a complete set of COP's and when they come in I'll replace them all and the plugs. Thanks, I am a newbie here and from what I've seen and the help it has given me, I'm staying...........Thanks a ton Bro

 

If you were throwing lean codes, you may also have a vacuum leak. Check the PCV elbow behind the intake manifold, that cracks and rots frequently.

Autozone doesn't have a clue.

 

Good to hear Doc, that you got a handle on the issue.
This was little known up to the time I had same issue on my 02 and went round and round studying it for some time and came to the final conclusion.
I observed here, the number of very specific complaints and how a miss was showing up and when.
This is timely now that I have about 5 years with my truck and nearly 100,000 miles. It has 132,000 on it.
Here are some further experiences and info.
I purchused a set of ACCELS and lost nearly all of them one at a time.
I believe they are made in China, so the qualty is very questionable.
The location of the coils on top of the motor is a very high temperature location especially just after shutting the motor off and having no airflow in the engine bay.
The coils are wound on a bobbin type of form with several seperations.
The wire is enamel covered. The expansion and contraction of the winding can rub through the enamel and cause shorted turns. It also involves the magnetic field produced around the core and it's reduction due to shorted turns.
The effects of this is lower output voltage or a lack of reserve voltage when needed.
Normally a plug only requires about 7K to 10,000 volts to break down the dielectric presented by the charge in the plug gap.
During very lean conditions this dielectric goes up and requires more of the reserve voltge the coil should have. It it's not available, a missfire occurrs.
To make this more clear, a coil may have the ability to output very high voltage but at the time of sparking, the coil is never allowed to give the full amount because spark occurrs at a much lower voltage level that stops/quenches the output at that point.
A note: don't get wild about claims from a coil vendor on super high voltages from their coils because a motor can only use it up to the point the spark jumps the gap and a little reserve for lean conditions. The rest is waisted and never improves anything but a higher possibility of leakage, plug tip and ground strap errosion. Said another way, advertising hype sells coils you don't need above the OEM design on a stock motor.
It is my opinion that even the OEM coils suffer from the heat and willl fail at some point in there life.
Took time to look into ACCEL and MSD official catalogs for 2010.
Guess what? Not see a listing for Ford cop coils for either vendor.
My guess is that there has been a high failure rate.
Places you will see them is in Jegs and Summit and other vendors under those names. Why I can only guess.
To this end, no one seems to makes a truly high end coil of this design for use in these high tempersatire conditions and so we have to accept failure at some time like any other part. The factory supplier seems to have the best ones at the moment but their failure should not be unexpected.
Now when it come to racing engines with high power, a better coil is called for mostly for reliabality in the application
Good luck.

 

Right - so you might as well just buy the whole set off Ebay for 80 bucks.

 

Ok the rest have now been replaced, as well as a full set of net Motorcraft plugs, Truck has not ran this well in a long long time. COP's came from Globe Automotive, for 89.00 and change, including shipping, plugs came from local auto store. Funny thing about the COP's, I compaired them to the stock Ford parts I took off, they all have the same casting and sprue marks, as well as the same mold ID's. The only thing I can see that is different is in the mounting hole on the Ford part is brass color metal, the mounting hole on the Globe part seems to be a sliver color metal, and on the Globe part the resin is not as deep as the Ford, and of course it does not have the white Ford part numbers stamped on the top. When you compare the price of each at about 137.00 + or - for the Ford part, 48.00 for teh Auto Zone part, 28.00 for the ACCEL part from Jegs, and 11.12 including shipping from Globe, it's pretty much a no brainer. No vacum leaks, Throttle body looks good and only required minor cleaning (did not have to remove) and my truck runs like new again. BTW, I use Lucas injector cleaner about every other fill up or so........Hope all of this helps somebody, if it does please spread the word, there is not enough known about this problem and it is often mis diagnosed as MAF sensors-vacum leaks, IAC, throttle position sensor, hell I have even seen it called trouble with the converter. Thanks for all the help bro's......Doc