1997 F150 XL 4.6L (6 code engine)

P0171 - Running Lean
P0303 - Misfire in cylinder # 3

I read through tons of forums, not just f150online.com, to determine how to fix this because I was buying a 97 F150 with these error codes.

I took the risk and bought the truck, I checked out all the vacuum lines and even some lines I couldn't identify. Finally I decided my first real attempt to fix would be to simply change the spark plug; it was a pretty quick and cheap job.

I am sure glad I did, check out the old versus new spark plug.



The old is missing it's electrode and from what I can tell so far, knock on wood, this solved my problem. So just wanted to put this out there for those running into this problem, this is one of the many possible fixes.

And from all my reading my order of attack to fix these trouble codes would be:

* Before starting remove + battery to clear check engine codes and "reset"
1. Vacuum leaks, look, look, then look again, then have someone else look (notorious elbow, PCV, etc...)
2. Spark plug change
3. MAF Sensor Clean/Check (Other sensors, O2)
4. Coil Pack check
5. Fuel Injector check (Other fuel related, fuel filter, etc..)
6. IAC cleaning / carbon build up
7. The rectangle box off the right hand side of the Throttle Body (can't remember it's name)
8. Intake Manifold seals (google search P0171 and see the google site)
9. Keep searching the forums

Other Cylinder Misfires Search Tags: P0301 , P0302 , P0304 , P0305 , P0306 , P0307 , P0308

 

Sounds like a good check list but how are you planning on checking the COP and the injector?

 

I have seen on a few boards on how to check the coil packs by ohm meter resistance test. Then for the injectors you could always swap with another one and see if the error follows the injector.

One thing that has bugged me on the boards is the confusion around what engines have 2 coil packs and which ones have a Coil Over Pack COP (1 per cylinder). My 4.6 (code 6 not W), has the 2 coil packs, but I see time and time again on the boards where people say theirs has the COPs. Is this just a misuse of the COPs term or do some 4.6's have this?

 

All 4.6 engine went COP by 2000 or 2001 I think it was All early 4.6 had coil packs. for sure 97-99. 5.4's never had coil pack always were COP ignition..

 

Let me comment on coils.
If a cylinder is out due to a faulty coil, a code is set and there is no question that the coil would be faulty because it will test open on either the primary or secondary windings.

A coil with shorted turns cannot be tested with an average meter either analog or diigital to see that fault.
The reason you can't see shorted turns is because the change in resistance is so small the meter will not show it besides the "tolerence range" of resistance from coil to coil is unknown.
The only way shorted turns could be seen is to know what the coil windings measures before the fault and what they measure after the fault on a test device called a 'wheatstone bridge'.
The failure effect from shorted turns is the huge effect on the magnetic field produced around the core that lowers the coil output voltage.
This type of failure was never addressed in the PCM program "directly", but is felt as a drivability issue under certain conditions.
A coil with this type fault is not a hard fault that will set a code because the PCM only keeps a short history of misfire, then clears the history out when it no longer sees the missfire, hence no code is set. Note, you would need a good mid level scanner to look at missfire history and may see a cylinder that has more history than others.
There is more to this fault but lets leave it at that.
Your dependence on other sources is not alway complete for info and experience..
Good luck.

 

i had a to lean problem my grandpa told me to leave coils and spark plugs alone and to remove change feul filter and check feul pressure if feul pressure was good enough then remove gas tank and clean the rust and water ect... and clean feul pump filter strainer but i didnt think grandpa new anythig about these sofisticated engines we have now with sensors and all so after spending a cple hundred dollars trying to fix the problem myself i finally done what he told me to do in the first and it fixed the to lean problem tank was rusty with water in gas matter of fact my gas in tank was a rusty orange color well when i finally got up the nerve to tell him what was wrong with it he told me you just learn 3things 1 you never know it all and 2 it pays to listen to someone who has been there and done that 3 engine parts nowadays are very expensive anyway i just figured i would share my to lean story hope you get yours figured out