P0171 - System Too Lean (Bank 1)

**siege101** · 11-10-2009

Vggggg

**BillBoost37** · 11-11-2009

Please search on "P0171" and my user name. Tons of good info already written up. It's early and I'm lazy.

**ZR1Vette09** · 11-11-2009

http://www.grandprixforums.net/vaccum_leaks.php

direct link, make it easy on ya

**BillBoost37** · 11-11-2009

Only problem with that write up is it leaves out the EGR tube, battery connections, gaskets, as well as a possibly faulty IAC.

**ninnyGTP** · 11-11-2009

Yup, was getting this code a few weeks back so I popped the hood and low and behold 2 vaccum leaks. Both were my fault haha. One was because I didn't cap off the line after removing the L67's MAP sensor and replacing it in the front of the motor using the L36 sensor. Other was the line by the battery leading to the tree on top of the blower. Fixed both and voila, no codes haha

**nault31** · 11-13-2009

If it's not a vacuum leak, have you checked the MAF sensor? I put one of those K&N oiled filters in my stock GT and it must have been over oiled from the factory because it dirtied up the MAF sensor and gave me a P0171 code. Cleaned the sensor with throttle body cleaner and I have had no problems for over 4 months now.

**grandprixgtdude** · 12-08-2009

Has anyone experienced any vacuum leaks near the throttle body. On my 02 GT is looks like there is a vacuum hose connected to the throttle body that then splits off into two hoses, one going to a tiny black canister and another going to another device. It looks like it is starting to crack and I am throwing this code but not experiencing any idle problems. It has been suggested that the fuel filter might need replacing. Any thoughts?

**BillBoost37** · 12-08-2009

Fix the known vacuum leaks first. Always fix known issues before you try to diagnose anything else in the system.

Fuel filter is possible, but it's not typically the issue.

**bladesrbetter1965** · 04-15-2011

Has anyone experienced the car literally lunging forward when letting off the throttle? It feels like I am slowing the car down by compression, like when you are downshifting. I to have the P0171 fuel system too lean on bank 1. Should I also be checking for the vacuum leaks, or is this a bigger fish to fry. I have 141,000 miles on this baby and the mileage has dropped from a steady 24.5mpg to 20.7.

**Bio248** · 04-15-2011

yep, sounds like a vacuum leak.

**BillBoost37** · 04-15-2011

Start with what you know is happening and then fix what's left after you get the obvious issues.

**ferret81** · 03-11-2012

I also have a P0171 Code and I checked and changed almost all the vaccume lines. I want to know id the Evap Canister can also cause this problem or no. my Car is a 98 GT 3800.

**GTP in RTP** · 03-11-2012

Originally Posted by ferret81

I also have a P0171 Code and I checked and changed almost all the vaccume lines. I want to know id the Evap Canister can also cause this problem or no. my Car is a 98 GT 3800.

Change the egr tube that goes to the lim. It will have a crack in it .Carb cleaner will not catch it and it is not visible without unhooking.