1998 Ford Taurus Lean Code Issue? P0174

ZUE

MEMBER
1998 FORD TAURUS
3.0L
V6
2WD
AUTOMATIC
160,000 MILES

I purchased many years ago a ScanTool device and had no idea what the data meant to me. I have a situation I am not fully understanding and I thought you might have a video addressing this issue. 02 Bank Any S1 is good. B Any S2 is showing Lean. STFT look spot on, LTFT is showing Lean at a +20 on both and STFT is showing excelant behavior. This confuses me to think that the CAT is not working correctly showing Lean making the LTFT go rich to compensate. Being in range the STFT looks good still. I am getting only a P0174 at idle, running temp.

3 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

Most of the time a lean code is set by a vacuum leak that would explain it being set at idle any uncontrolled air leaks the computer sees as lean condition. The first thing I always look for when I see lean codes is a vacuum leak and most of the time thats what I find causing the code.

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Monday, January 19th, 2015 AT 8:17 PM

ZUE

MEMBER
76 POSTS

Wow, I really forgot the important stuff here. I ran a smoke test looking for the vacuum lean and found very small leak around TPS and EGR Valve. I fixed those but the results were unchanged. Leaks were too small to make a difference. I am really trying to understand a secondary O2 giving a lean signal off when the primary O2s seem to be reading fine.

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Tuesday, January 20th, 2015 AT 11:06 AM

SATURNTECH9