CSprain

That is helpful. I will check the ohm reading as soon as I can. Probably won't be able to until tomorrow unfortunately.

haha

Are you sure you seated the coil and boot properly on the plugs and didnt bend the coil inside the boot?
Dont know if that would cause a problem. Just throwing it out there.

I know when I did my plugs, the cop's against the firewall were a little tricky to get in and make sure the coil and boot sat right on the plug.

CSprain

I tested all the coils on the cylinders that were misfiring. They all test at about 1.0 ohm. I moved the coils around and still have a misfire. All the boots looked new. No cracks or anything. I am going to go get a snap on mt2500 tomorrow so i can see what cylinders are misfiring whenever I want. If the boots look good and the coil ohm reading is correct is there any other way to test the coil? A chance to see if it is failing? I have fresh plugs but I will pull them and check the gap on the plugs hopefully Wednesday. Thanks for any input.

k7780446

Mine is doing this as well but mine won't get above 45 and I had it toed to a shop. I have a 5.4 saleen supwechharger on mine though. It runs rough at idle and codes read running lean on bank to and misfiring on passanger side I believe

TexasKid747

In addition to the 1 OHM resistance at the Primary side of the coil (on the 200 ohm scale), I measured the resistance from the Primary through the Secondary, meaning to the tip of the contact at the plug end of the boot. On the 20,000 ohm scale the resistance was 5.7 to 5.9 if memory serves. I also stretched the springs out a little since they do not protrude to the end of the boot like a new one does. They are close, but as much as 1/8th of an inch shorter from being compressed for 165,000 miles.

Then, when installing the coil pack I turned it so that the mounting lug was not over the screw hole which allows you to press the coil further toward the plug. This was to "force" the spring onto the plug. I do not know if this is possible on all plugs, I only removed three. (cylinders 5, 6 and 1)

I guess the last resort is a spark checker. I've not used one but that confirms spark is present. Of course, mine was so intermittent that the Diagnostic computer may be the only resort.

CSprain

I will try that method for putting the coils on. And I would like to use a spark test but haven't had anyone who could turn the key while I watch the spark. I will pick that scanner up today and see what cylinders are misfiring and give you guys an update.

DTeal210

I had the same problems with mine after a plug change. After several evenings of diagnosing things, I found that one of the brand new plugs had a hairline crack in the porcelain. Put a different plug in, and it was good to go!

So you might look at the plugs one more time.

CSprain

I definitely will look, thanks.

CSprain

So a little bit if an update. I took all the coils off and checked the prongs and boots. I used more dielectric grease. I made sure to get a good connection to the plug. And now no more misfire. No more rough idle. No more shake going down the road. I did end up taking it back to the shop to have them ensure there wasn't a misfire. Shop fees totaled $170 so not too bad. now just a few small things and the truck will be good to go. I really appreciate all the help.