^This

 

If nobody minds - can I think out loud a little more about this? I'm thinking these 'rich' / 'lean' terms related to O2 sensors detecting presence of Oxygen - and fuel either getting (or not getting) mixed with it - and /or all burned up by combustion -- is scrambling everybody's brain. And is about to cause a parts throwing party here.


I believe @PerryB has a valid point - but partly for the wrong reason. (cause & effect). The BIGGER point is the P0171 code can itself be the direct cause of the misfire for a number of reasons. I would recommend ---- Address it first. Could possibly be as simple as a vacuum leak. The PCM's reaction to a vacuum leak is to 'lengthen' Fuel Trims. Plug nearest to the leak (if IM gasket) could be too lean fuel mixture and misfire. OR the resulting increased injector pulse widths could be 'flooding' the weakest plug from TOO much fuel in the mixture. OR as @PerryB suggests - a defective injector. (They can be sticky/defective either direction - Opening or Closing). Which ever - no use in throwing COPs, Boots, Springs, or plugs at it to see. [Like we said - just thinking out loud here]


A 'lean' condition (O2 sensing unburned Oxygen) is reported by the PCM because Fuel Trims exceed the "+" limit.




Motorcraft OBDII Theory of Operation manual, page 30

 

Cheaper yet, swap the #2 COP with the one next to it, and see if the problem moves. If it doesn't, you'll want to decide whether to try a new plug or injector next, IMO.

 

 

Clean tips of cops, exchange with adjacent cyl to see if code moves . Fairly quick, cheap effort . You could also find some loose plugs if someone didn't torque them to 25 to 28 pounds .
If vacuum leak suspected ,a homemade smoke machine off you tube can do the trick . Lean does suggest a vacuum leak among other things .
I never had much luck with after market coils .
I had to change all my injectors around 120k . Its a pain to pull fuel rail , it tends to get gas every where and that can damage boots . Plenty of rags are needed and i clean all the surfaces that the new orings touch, not really labor saving to change one injector if you have a lot of miles on her . But they are not cheap .
Let us know what you find as we are all still learning .

 

Just got home from a long stint at the hospital...Picked up the COP insulator boot and spring on the way...Popped the hood and got the bejeezess shocked outta me... A WHOLE lotta stuff in the way, how much can I move ? What's the big pipe going over the top of the COPs on side 1 bank ?...I know these are ignorant questions, I just really don't want to mess up...My old '92 was a breeze compared to looking at this...

 

That's the fuel rail. The coil will come out without having to move much, just make sure you don't drop the 7mm bolt holding it in.

 

Above and left of the fuel rail....Rubber hose coming out of a fitting forward of the COPs , runs above and just left of the front 2 COPs then curves over #3 and #4 towards the firewall...My light is out, looks and feels like it goes into the firewall...

 

Pictures...? I did 6 of the 8 coils without moving a single thing. The back two are a little trickier.

 

Figures, my camera battery is dead and looks like it's not taking a charge.....If you have a Haynes manual on these, pg 1-4 , just to the right of the trans dip stick....