97 f150 4.6 missfire problems

ok a friend of mine just bought a 97 f150 ext cab 8 foot bed with the off road pkg its got the 4.6 with the auto trans and 4x4 and 116k miles the thing ran and drove very nice no unusual noises and seemed to be kept up 3 days into him owning it we were on the highway and the check engine light started flashing we got it home put it on a code reader and it said a miss fire on cyl 3 and 7 we brought it to the stealership they said he had 3 bad injectors for cyl 1 3 and 7 and gave him a quote of nearly 1200 to fix itso we had my mechanic fix it but 3 new injectors in still has the missfire changed the plugs for those 3 still has the missfire for cyl 3 ran a treatment through a tank of gas STILL has the missfire replaced both the coils STILL has the missfire so at this point any idea's or people that have had a similar problem please offer up any ideas thank you all in advance:banghead:

Does it have COP's (coils on plugs) ?

If so replace #3 & #7.

Does it have COP's (coils on plugs) ?

If so replace #3 & #7.

i dont believe so i believe it is just the two coils up front

My 99 f150 V6 did this. It would run rough sometimes and sometimes not. Check eng light would come on for awhile and the go off for 3K miles. Ended up being the plugs and the wires. They are probably the original wires. Check for cross firing on them. I found mine buy accident while having the hood up at night. In the dark you could see the spark jumping around where it wasen't supposed to be. No trouble since changing everything.

My 1997- F150 - 4.6 had the same problem. The fix was new wires. The coil packs at the front of the engine on both sides usually don't go bad.I have 146,000 miles on my truck and have never replaced the coil packs..

MIs fire on #3&7. More than likely it will be your coils, they aren't that expensive. The check engine light flashing meant that you had a primary ignition circuit failure. I would disconnect your harness from the coils and the PCM. Read them out to makesure there is no high resistance or intermittent beak in the wires. If they check good then replace the coilpaks that control the said cylinders

i am having the same promblem with my ford but my is 2,4 and 8 cyl doing the misfire codes,have you got yours fixed cause i have tried everything i have been told to do and to replace and still having the same problem