1997 Ford Crown Victoria - 4.6/auto - 103K miles

Check engine light appeared on Monday. Had the code read, P0174 Bank 2 too lean. From what I'm reading the too lean code can be a number of things, MAF, PCV, vacuum leak, fuel pump or filter, oxygen sensors. But I'd think that if it was the MAF, PCV, or fuel delivery, it'd probably effect both banks, right? I've dealt with vacuum leaks before and generally the car starts running like shit; this time other than the light it seems to run fine. So that seems to leave the O2 sensor (Bank 2 upstream). Not an expensive part but kind of a pain to get to. Does that sound like the culprit or is this worth buying a code reader with live data and checking more thoroughly before I throw parts at it?

Thanks.

7/23/2014 2:43:16 PM

you could take it to a shop and have them test the O2 sensor

7/23/2014 2:58:01 PM

Correct thinking about ruling out common denominator culprits that would affect both banks. Too lean condition on one side can be caused by a few partially clogged injectors, intake manifold leaks on that side (most common issue IMHO), or bad upstream 02 sensor. While some would dismiss it as snake oil, I would run a bottle or two of Techron concentrate or equivalent to see if it clears it up. For $7ish, its hard for me to ignore it at that stage compared to a $100 sensor and the bitch session of labor reaching it. After that, look for any hoses/etc on that side of the engine after the MAF that may be cracked or loose. And while you would usually get a code for an out of range or bad sensor check all wiring connections to it first. O2 sensors arent cheap and while I wouldnt rule it out, it wouldn't be the first thing on my list to replace unless you had a shop with the right scope/software and tools to tap into it to confirm a bad sensor.

7/23/2014 3:02:40 PM

Going to check for vacuum leaks definitely before doing anything else. Also might try the techron in case it's partially clogged injectors.

The sensors for this car are actually pretty cheap ($28 for OEM from rock auto). But the labor is not inconsequential plus I don't have anywhere to work so I'd have to borrow a friend or family member's driveway.

Evidently, from one site, if you get a scan tool with live data there's a way to check the +/- values on the O2 sensor and depending how they respond to a little spray of carb cleaner, determine if it's working right or not. Debating whether I'd have enough use for the scan tool afterward to justify $80 (Considering the Actron CP9575).

7/23/2014 7:38:15 PM

It's been over 10 years since I took autoshop in high school, but I remember checking O2 sensors with an oscilloscope. Is that not how you check them?

7/24/2014 9:17:48 AM

o-scope? wut

we pulled out that arcade-game sized unit to 'show' how to set the dwell on an old ford v8 one time, when I was in Auto Tech.

7/24/2014 9:23:33 AM

http://www.ngksparkplugs.ca/tech-info-oxygen-sensors.cfm#os3

i guess a multimeter can also be used

7/24/2014 9:32:00 AM

Forgot to add an exhaust leak is worth checking out, can also cause the code.

Check out scantool.net , had good success/customer support with one of their dataloggers/ readers for about the same money for a non-professional like me. Came in handy for diagnosing intermittent emissions issues I've had in the past.

7/24/2014 11:30:34 PM