Well after reading this forum for a couple years I finally broke down and joined.


I have a 2000 F150 4.6L/Auto. My dad bought new, I bought it from him in '04 with about 80k miles, 9 years later I am at 113K miles.I drive it very little as it is pretty much my hunting/fishing truck. last summer it started skipping going up hill's. The computer code was low EGR flow, after searching on here I found that the EGR port on the intake was clogged with carbon. I took it apart and cleaned it really good, it started working good, about two weeks later the skipping came back. Then I got a another error, cylinder 5 misfire, so I replaced the Coil over plug on number 5, a few weeks later, the problems returns the cylinder 3 misfire. I replace the Coil over plug on cylinder 3. Also while doing this I replaced the fuel filter, and all the spark plugs. It has ran good since I completed all listed above, last weekend I had to tow a car for about 30 miles. During the tow the skipping came back and the error code shows cylinder 5 misfire. This cylinder has a new plug and a new (motorcraft brand) coil over plug with only 300-400 miles on it. What would bring all this back, I have heard that once one COP goes bad then to replace them all, due to others failing, but why would a new one seem to go bad. Also I Ohm'd out this new coil and the two old ones, they all measured the same, 5.5k ohms between the spring and each contact, and .65 between the two contacts. My hayne's manual states they should rean 5.5k and .55 Ohm's, but does not give a tolerance range. Also the truck just seems to be weak in general. Sorry to be long winded, I just like to cover all bases and to be clear of all work completed. Thank you in advance.

 

Your just having a run of bad luck.
Coils and boots are replaceable parts just like shocks or tires that can go bad at anytime.
Maybe the connectors are not being firmly set in place.
Maybe the cats are plugged from overheating as a cause of poor power.
Measuring coil resistance is close to being worthless because you cannot detect anything but opens or shunts.
The PCM tells you when that happens so you don't have to try measuring them.
The problem that can happen is 'shorted turns'. You cannot detect them with a meter.
The best way to see the health of the ignition system is to use a Scanner capable of looking at diagnostic mode 6, test 53.
This looks at the misfire monitors history for all 8 cylinders.
This will show bad boots, coils and plugs on all cylinders before any outright failures even occur that set a code.
Keep addressing the codes as they come up because any replacement part can go bad.
Eventually you will get to a point it all straightens out.
It's called nickel and dimeing you to death until you get all the issues cleared.
You have no other choice.
Good luck.