1997 F150 XL 4.6L (6 code engine)

P0171 - Running Lean
P0303 - Misfire in cylinder # 3

I read through tons of forums, not just F150forum.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

 

I just had the code P0171 last week. (and P0174) There is an easy fix for this one. You should clean your MAF, and prolly also change your fuel filter. Those fixed it for me.

As for the P0303, Im not sure. Maybe with the stuff you done that will be fixed.

 

Not sure why I can't edit my old post, but here is the pic that fell off -