too lean

I have a 2000 f150 4.2L. The service engine light came on, so I had it checked out. It turned out to be p0171 bank 1. I put injector cleaner in it and drove all weekend. No service engine lights came on. Untill today, I was just about home then bam. So, when i got home I pulled a couple of plugs and they are white. It seems to be a fuel problem, but it is running great. What else could be causing this?

Two common things will cause this, a dirty MAF sensor, and a bad HEGO sensor.

Dirty MAFs come from K&N filters, DO NOT use them.

HEGOs just die for no apparent reason.

It is possible that you ahve a vacuum leak, but that is easy to check with a can of ether (starting fluid) sprayed carefully at the intake where it meats the heads with the engine running.

This is most likly a vacum probelm. I had this probelm once and the vacum tub coming from the iac to the head was not connected. Check all your vacums.

This is most likly a vacum probelm. I had this probelm once and the vacum tub coming from the iac to the head was not connected. Check all your vacums.

forgive me if i am not up to date with the acronyms, but i am not sure what iac stands for. please enlighten me

The IAC is the Idle air control. It is located near the front of the troodle body. From where your air filter is and follow the tub back. You will need to take off the dust cover that is over your troodle body and there you will see smaller tubs that go different places which are your vacume tubs. Also I would change out your pvc while your at it. Cheap and easy. If have the energy I would take of the air intake tub and clean the mass air flow sensor. Be sure to use sensor safe cleaner only.