Joined: May 2010
Location: Berkley Township
I now also have a 4.6 GT and will be doing a plug swap soon as I like the Irridium Plugs... Anyway... before this I had a 4.0 V6... I stupidly installed a set of E3 plugs and it ran good for a couple of months. One day on the way to work, wham, out of the blue it started to run so rough it almost through me out of the car, but it did not through a code and did not light the check engine light. Anyway, inspecting the plugs, they looked terrible, so I got a set of Bosch Irridiums and a new set of wires and put them on, and the car ran great, better than ever.
I mentioned the fact that it was running so poorly to a mechanic I know, and he said that Ford decided, in their infinite wisdom, not to bother with misfires like GM does with their computers, and thus there was no permanent or temporary code. I thought it funny that the Oxygen Sensor should have gone nuts and thrown a code, but no it did not. I then remembered a similar problem I had years before with a Turbo PT Cruiser. One of the injectors hung open and it was running rough and smoking like crazy, but again, no check engine light and no code... Hmmmmm. Took the dealer two weeks to figure out it was an injector, as he said it held pressure and everything, but they replaced the four injectors on the four banger and it ran great.
So.... bottom line, PCM's and the OBD II are great tools, but can not always troubleshoot every problem. Experience seems to still be the key in some instances. Good luck with resolving your problem ...... Hope you find it soon and are once more driving around happy as can be.