I drive a 2001 F-150 (5.4 V8) with about 143,000 miles on it. Sometime early in January I went out start it to go to work. I noticed it was vibrating really bad as soon as it started. We had it towed tot the mechanic and he said a cylinder was misfiring due to a broken ignition coil. So they replaced the ignition coil, problem solved.... for 2 weeks. Same thing happened again, replaced another coil. 3 days later same thing happens again, so they replace all the ignition coils. Problem solved... until last night, coming home from work, the thing starts vibrating again. I'm taking it back the the mechanic today, I have a feeling its the same thing that happened before. The guy is a friend of the family we have been going to for 30 years so I doubt he is messing with us. Anyone heard of this before? or know what the heck is going on?
And I am fully prepared for all the "ford's suck" jokes about to come my way.
When you say vibrating, I would also assume you are also getting an PO30X (1-8) misfire code from the PCM?
Is the vibration steady or only at certain speeds, certain loads?
The COP for 01 only has one water-debris retention ring on the Coil pack itself. When you pull a coil pack for any Modular family motor, just under the coil assembly itself where the boot starts (the area that goes into the head) will have a single or series of three rings for sealing. Single ring COP's don't last as long as the latter Three Ring units (Ford updated the design in late 02) and will fail on other cylinders besides the #6 and #3.
Also, you need to check the plug(s) for traces of carbon arcing on a COP that went bad. If you look at it closely the porcelain of the plug, it will have small black spider web like traces on it. Swap the plug if that occurs.
When a Coil Pack is reinstalled, it is also important to make sure that the COP boot has a good coating of Dielectric Grease inside of the boot as well.
If you are not getting a PO30X code indicating misfire, you might just have a shuttering torque convertor which is common the trans if you have went over 50K between servicing it. That will cause a buck-shudder at 45-50 mph under a light tip-in throttle in Overdrive.
Just as an FYI, Modular motors don't blow plugs from the #4 (or any hole) just because. What happens is the Mass Air Flow meter starts to fail, this causes an intermittent extreme lean condition usually on #3. Those cylinders actually have a single point overheat in the combustion chamber which expands the cylinder slightly. The plug machining onto the head was never deep enough and the plug can work its way out.
The issue is most prevalent on 4.6 Police Interceptors and certain 5.4's Trucks where the driver uses WOT (wide open throttle) quite frequently.