I've got a 97 Expy 5.4L that I've been working on. Did a tune up on it (plugs/wires) b/c of a slight sputter, poor perfomance. The old plugs were completely fowled out. 1 day after doing this the check engine light came on. Did a diag. on it and it was missfire in #2. Checked the plugs, switched coils, swithed injectors, coilpacks, ohmed all the injectors and coilpacks, put everything back together and the mil light went off. Driving it 2 days, mil light did not come on, but it still has a slight sputter that wasn't there before. Any suggestions?
Thanks,
SilverNCSU

 

By the way, I read a previous thread mentioning the wiring harness rubbing against the a/c compressor and in fact it was. Tied it back, but still sputters when under strain, going up hill, etc... I also read a previous thread about the fuel pressure reg. being bad. Fuel pressure is good. Also has good compression.
Thanks,
SilverNCSU

 

You don't mention which plugs you used; consensus is that they run properly only on MotorCraft platinums.

Something else you might try is to dose the fuel system with SeaFoam. Heck, dose the oil system with it, too.

My '97 Expy and '99 F-150 (both 5.4s) respond well to the treatments.

HTH