I just changed oil and cleaned K&N filter, I have 99 f-150 with 59,000, changed fuel filter last oil change, so I cleaned Maf and still getting codes, should i be looking for a vac leak, also changed pcv last oil change, had same codes 3,000 miles ago, all has been good till know , any help? thanks

 

With both banks showing lean, check that the K&N is not over oiled, and coating the MAFS wire.

How did you clean the MAFS ?

When you put it all back together, did you check all the lines to the intake elbow to make sure none are pulled part way out ?

Is the IAT sensor installed completly ?

It is easy to put it together and have one look like it is on, but it is letting in un-mettered air, cposs causing the lean condition.

The main ones as of late seems to be either clean the MAFS or the cracked elbow on the back of the T/B for the PCV.

This is why I asked how the MAFS was cleaned, and to make sure you don't have an over oiled filter installed.

If the MAFS is still clean ( and the filter is not over oiled ) next is to check the PCV elbow on the back of the T/B for cracks. When you go to get this part it is a new elbow, tube and PCV as a kit.

There are other things, but these seem to be the first ones to check on. doing a search on P0171 will show 36 threads with some of the results posted back from other members.

Post back with some results.

Good luck

 

I clean the maf buy spraying some electrical cleaner on the wires, i do not take maf out just undue filter housing and spray, I do not think filter is over oiled only spray small amount, as had that problem before, i lookded at my pcv vac line and it seems to be all one piece to back of tb no elbow?? thank for the info

 

all is good, found vac leak from pcv valve, no cel , thanks for all the info!! this site is great