I have a 2007 EXP EL 5.4 4x4 and at 45mph with the cruise set, when you slowly accelerate (most noteable with the cruise button) it bucks and makes a clunk like the transfer case or the drive shaft is getting hammered. I had Ford test the coil packs after reading on here that they can misfire when they get weak. They found that 1 and 7 were dropping out so I replaced them with FOMOCO coils and the problem was still there just not a severe.

So I went back to the garage and they tested it while driving and found 3 was dropping out. I replaced #3 and the problem is still there and I would say just a bit worse than before. I am tempted to just replace the rest of the COP's but not sure as this seems weird that after you replace one a new one drops out that did not show up on the test just 10 minutes ago.

Any suggestions?

Steve

 

I have 67k miles on it just bought it used a week ago

 

You should consider doing the plus too. Similar story here - 2 weeks after purchasing my 07 4x4, same thing. I replaced all plugs and coils and it runs smooth as can be now. I did use motorcraft plugs but chose to use Accel COPs.

 

+1 on changing the plugs. yanked some champions out of ours that the previous owner had just had installed 5k ago and they were toast! The Motorcrafts went in and no problems since.

 

Champion spark plugs are crap. Use only motorcraft. I found that out first hand

 

Use only motocraft plugs. COPs are hard to really test. They fail slowly while causing issues. I would replace all COP's at this point to rule them out and go from there.