Richard55

My 2003 Expedition 4.6 with 95,000 miles is missing and back firing I get all kinds of codes, but consistently P0171 bank one too lean. I have been to private and dealership mechanics and so far piece by piece have replaced.... all of the oxygen sensors, the EGR valve, the 90 degree rubber boots that crack, the pcv valve, intake gasket, coil pack #5 (all the rest tested good), the catalytic converter, fuel filter, air filter, cleaned the mass airflow sensor, had the fuel injectors checked (all good). At 50 driving down the highway it runs the best but still misses. Idling and low speeds it is the worst. None of the parts I've replaced have made a difference. I'm out of money and the mechanics are out of ideas and input would be greatly appreciated.

R.S.LOGAN

Checked compressions ?

Bert

R.S.LOGAN is correct, check the compression. Have you been going to a different shop every time? Have you told any of them it hasn't been fixed? Was it still running the same when you got it back from them?

__________________
Bert

Richard55

I've given each of the shops 3 tries before I give up on them, letting each know that it wasn't fixed. I give the next shop the run down of what has been done. The most recent was a ford dealership who's master mechanic had it for diagnostics for a few days. They were "positive" it was the intake gasket. No go. Then they were sure that coil #5 was it - Not it again. I am supposed to take it back for try #4 but I am losing confidence. I called ford customer relations who suggested trying another dealership - starting over with another $88 diagnostic fee. I've been to Autozone inbetween to check if anything has changed with the error codes.

I will check the compressions and post.

Hamfisted

Well bank one is the passenger side bank. Cylinders 1, 2, 3, 4 (front to back...). So I would concentrate on that side. Do you hear any odd noise from that side of the motor ? (like exhaust leak...) . I'm thinking vacuum leak, but you said they already replaced the intake gasket right? You might still take a spray can of carb cleaner and spray around the intake area and see if the idle changes.