Code P0171?

EARL91

MEMBER
1999 BUICK LESABRE
3.8L
V6
2WD
AUTOMATIC
170,000 MILES

I have the car listed above (limited model) obd2 indicates Code P0171. Car is running too lean. I have replaced the fuel pump and sock. Replaced fuel sending unit new fuel filter. New O2 sensor bank one. Now the check engine light is flashing, and the car still sounds like a misfire and running rough if it runs at all. I replaced plugs wires and coil. What could be the next step to fix it? Please help.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,740 POSTS

Hi,

If the check engine light is flashing, that indicates a misfire is occurring. There should now be additional codes. Let me know what they are.

Now, in most cases, a lean mixture is the result of an engine vacuum leak. Have you checked for leaks?

Here is a link that explains how to check for leaks:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you look below, I included the diagnostics for the P0171. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.

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Friday, October 21st, 2022 AT 10:22 PM

EARL91

MEMBER
88 POSTS

Could my fuel sending unit not being sealed properly cause a vacuum leak?

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Sunday, October 30th, 2022 AT 7:40 AM

JACOBANDNICKOLAS

MECHANIC
109,740 POSTS

Hi,

If you are referring to the sending unit in the fuel tank, I would say no unless there is a hose off to the EVAP system (charcoal canister.)

If you look below, I attached the vacuum schematic for the evap system. I tried to highlight where vapors go, which wasn't simple because my highlighter is too big. LOL

Anyway, that is about the only thing that I could think could happen if there was a problem in that area.

Let me know.

Joe

See pic below.

Image (Click to make bigger)