I own a 4x4 '98 Ford Expedition with 99k, with the 5.4l engine and the 8 little coil packs (I hate 'em). About two weeks ago started experiencing a little missing and bucking which has gotten considerably more noticeable recently. Twice now the engine started bucking so hard I thought it would come off it's mounts. I can pull over and restart and it's all good for a little while, then it starts again. Check Engine light came on and gave me codes for Cylinders 4,5,6, and 8. This seems a little fishy to me, as I have been told by a Ford Service Manager that he has never seen more than one or two coil packs go out at a time, and usually because someone washed down the inside of the engine compartment. Anybody know anything else I should be looking at before I go the expense...and the TIME to change out these packs...especially 4 and 8

 

well the time really aint too bad, but the expense is pretty hefty, its like 80 bucks a pack right?

In any case, im kinda curious if you really have 4 bad coils or not. I believe detecting misfires on a per cylinder basis is done via the cam somehow and im thinking maybe theres a problem seeing which cylinder is bad there. Im hesitant to believe you engine would even run with a misfire across 4 cylinders. Do you perhaps have a buddy with a 5.4 you can test your coils on?

 

Nope don't have anyone else to test coils on, but I have been reading posts on people cleaning out their engine compartments with pressure hose, and having 6 out of 8 coils go at once, because of water standing around coils. I haven't done that but we did have flood conditions around here a couple of weeks ago, and I did have to drive through about 15" of water, thought it was fun at the time but.....could be my problem. Don't know why FORD would design the engine block to hold water like that in a 4x4 but they did.

 

I know there is a resistance test you can perform on the coils to see if they are bad or not but I don't have the procedure handy. If someone could post the test procedure you would have to pull each one and check them out. If you do need to replace any of them, try the following website:

http://www.fordpartsonline.com

The last time I checked they sold the OEM coils for around $60 each. (Their site is down at the moment) They are a regular Ford dealership but put their parts department online and sell OEM parts for much cheaper than you can get at your local stealership.

 

I replaced all four cops, and the fuel filter. Did the fuel filter first as it is the easiest and cheapest to do, drove the truck, no difference. Replaced all 4 cops, and HALLELUIAH!!! Praise God!!! It is fixed. Tested all four "bad" coils and cylinders #5, #6, and #8 did indeed have bad coils (resistance should be around 5500 ohms or less, it was over 7000) #4 though tested fine. Couldn't figure out why I got the code for 4 until I looked at the firing sequence. It fires the cylinders in this order 1,3,7,2,5,6,4,8. I guess because 4 is right in the middle of the three misfires it may have been affected also.