My 97 5.4 has been great for over 108,000 miles and I started having a misfire on #4 problem. I changed the plugs which were all in good condition and still had the problem. It turned out to be a bad coil pack. I replaced it and it ran great for four months. Now I am experincing the same problem on the same cylinder. #4 misfire. I replaced the coil pack again and three days later it is misfiring on #4 again. Does anyone have any ideas? I think it is the wiring. I believe if the computer were bad it would store a code. Anyone else have this problem?

Help!!

 

Tony,

Somewhere on this forum people have complained about this same thing and I think that they isolated to a coolant leak from a heater hose. Do you get any coolant wetting the #4 plug and coil?
I could be wrong about this, but its worth a look anyway.

 

crashz is correct on this one!

Look just above the #4 coil and you will see a rubber hose attached to a bent metal tube. If there isn't a screw type hose clamp on it that is most likely your problem. Very common on your year 5.4

If there is a screw clamp give it a 1/2 turn tighter.

 

Thanks for the inputs. I did find the clamp you refered to and it didn't appear to be leaking. I did get 1.5 turns on it though. I replaced yet another coil pack. That makes 3 in six months. Now I just have to wait and see.

Thanks again.

 

My father has a 2002 F150 4.6L. He had a misfire on #3 and #6 cylinder according to autotap. I took the coil packs and moved them to different cylinders. The misfire then happened only on one of the cylinders I moved the coil pack to. I hope he doesn't have to replace these too often. The coil packs are $68 each. The truck only has 55K miles. There is no water dripping on them.