I have a 1999 F150 SC w/ a 4.6L, a 5 Speed and 35K on the odometer. The vehicle is outside of warranty. About two months ago, I got the dreaded "service engine soon" light. I took it in to Autozone to scan the codes. Scanner reported PO172 System Too Rich (Bank 1) and PO175 System Too Rich (Bank2). The Dude at Autozone suggested I replace my air cleaner. I have an AirRaid System that had about 25K miles on it so the K/N filter was quite dirty. I cleaned and reoiled it then had Autozone clear the Codes. "SES" light stayed off. No issue for two months. Yesterday the SES light comes back on. Scan the codes at Autozone P0172 and P0175 again.

Does anyone have any insight on what I may do to correct this?

BTW, today the Autozone Dude wouldn't clear the codes this time as he said it was a liability issue.

Thanks in advance for any help you can provide.

Rob

 

Yeah, liable that the BBB may find out how much they're ripping people off.

I would inspect the MAF sensor for trash and oil on the sensor wires.

 

With you getting bank 1 & bank 2 lean codes I would suspect the MAFS, the EGR or a vac line.

Here is a thread that posted the Ford service manual "to trys" on the codes.
https://www.f150online.com/forums/sh...hlight=P017%2A

The Problem soultion section for both P0172 & P0175 point to the list in P0171, so this is the list.

If you do a search on P017* you will find a list of posts on this, if you want other options to try.

Take a look at Jeff Laws post ( kidtriton ) on the PCV elbow for a cracked line if cleanign the MAFS is not doing it for you ( unless the MAFS is dirty again ).

Steve