Dough

Ok I know this is an old thread but when I went to test my coils over plugs I got confused. The original COPs had some blunt end insert at the end of the spring so rather than the spring sliding over the end of the plug the flat end of the insert rested on the top of the plug. I bought replacement COPs and these didn't have the flat end insert. Also interesting, when I did a resistance check on the original COPs the lead to the ohmeter was touching the flat end of the insert and with a value of 8.1. If I removed the boot and touched the lead directly to the spring (of the cop) the value was 5.5. Right where it should be. When I checked the value of the new cops (that did not have a blunt end insert in the spring) the resistance value was 11.0. So what is the insert in the original cops and what does it do and why doesn't the new cops have it too? Also, does the high resistance of the new cops affect the operation of the motor? I checked for of the new cops out of 8 and all 4 tested read 11.0. If all have the same resistance does that affect the operation of the motor? Dough

SAndrew26

Don't worry.
Insert should be a resistor - coil always has a resistor to reduce EMI (electromagnetic interference, so your radio still can pick up a station). It looks like the new coil has internal resistor, so you don't see it in the spring.
Total resistance is not important (well, if it is 10 times off, then you may have a problem). Manufacturer may have chosen slightly higher voltage and slightly higher resistance - so the spark current is the same. +/- 30% should not matter, unless you are a racer. Repeatability is more important - if all readings are the same, it indicates good, repeatable and well controlled production process, which usually means better product quality.
Bottom line - don't worry.

Dough

Thanks tons. Can't tell you how much this helps!

westtnfx4

Edit: sorry i forgot those old 4.6's had coil packs insted of cop's)
Here's the way I test them....start the engine and let it idle. Unplug each coil one at a time. If there is no change is the engine running/idling then there's your dead coil. If you unplug one and it starts to miss and shake you've got a good coil. Works everytime and I use this on my own trucks. I got this tip from a mechanic at the Local Ford dealership about 10 years ago.

Jamie 213

dont you get a shock? and if not what do I unplug?

Dough

I proceded to install the new no name coils (made in China as it turns out) I bought through Amazon. I could only get to 6 of them. I don't see how anyone could get to the ones closest to the firewall. I can barely see them. I'd like to see a Youtube video of someone doing those last two. As it was the 3rd from the the front on the driveres side took me 3 hours by itself. The fuel lines right aboove the coil hold down bolt had some vacuum actuator right above it. before the bolt was fully screwed out the top of the socket/universial "topped out". I couldn't turn the bolt the final 6 or so threads. The space was so tight a wrench could barely swing. I tried every position. Man. I rubbed the skin off my fingers, both hands, trying to get that out. Putting it back was even worse! There's probably some special $150 tool that I don't know. Should've of cut off my thumb and two finges off or used a 14 yo with very skinny arms and hands to reach it.

I as I took the old ones out I tested each of them. Some had the resitor some didn't. All but one tested with 5500 resitance. The one that didn't the meter kept bouncing from 4,000 to 8,000. Anyway, with the 6 new ones in place (with the 11000 resitance) the truck is running much much better. I still have to "hill" test it though. I'll pay someone to change the last two. No one should face that abuse!

esumerfield

I have been experiencing a missfire when accelerating, at idle (crusing) or at a hard accelerate its fine. If the truck downshifts I don't detect the missfire, only during roll on in the same gear. I suspect a bad coil but am not sure if it will show up using the standard testing...I was going to buy 2 coils and just rotate them till I find the problem.

There are no codes being thrown, and I have already replaced all the boots, any other suggestions, or something else I should look at before doing the coil replacement??