I have a 97 expedition with 5.4 engine....i keep getting cylinder 3 misfire code ...the engine runs perfect while idling upon acceleration it starts missing and CEL starts flashing....i have put it on the computer at the dealer....everything checks out fine ...compression check, fuel pressure..etc..

i changed coils from #3 to #1 and still shows #3 to have misfire....i am ready to pull my hair out....lol....any help would be appreciated.

 

Have you traded or replaced spark plugs?

 

I have to second that. I tried to track a miss fire for some time. The sparck plugs had just been changed about a month before that but the problem was a plug the was cracked when it was put in. At idle or slow to moderate speed it was fine. Finially changed it and I have not had a problem since. Even when the shop put it on the computer it showed fine at idle.

 

Another problem could be a partically clogged injector. Giving enough fuel at idle but higher rpm's it starves. However I would check the spark plug first.

 

i had the same problem on my 99 4.6 i replced coils sparplugs wire nothing i then replaced the egr valve and that did the trick for me no more misfires hope that helps, but on my truck everytime i went to step on gas cel will flash and it was bucking like crazy changed egr valve solved my issues good luck.

 

I put new plugs in....same result...i am leaning toward injector myself....gonna change injector and see if it makes a difference...thanks...will let you know the results.

 

Remember to disconnect the battery for at least 15 minutes to clear the codes. Otherwise the #3 misfire code won't go away.

 

did u try on replacing the boots on the plugs