: P0171 to lean code?



speedydog
04-27-08, 10:18 AM
i have a 2001 sts, just had p0171 code(to lean bank 1) come up for second time in a month, i erased first time, i had replaced my crankshast sensors about a month ago, it come on then so i erased it changed sensors because of the commen problem of die out ,wich is cured now never had the relearn procedure done (per advice on here ) the car seems to run ok little rough idle when cold but always seemed that way car has 67k on it any thoughts ??i,ll go look for vacum leaks now, but i did not hear any when i opened the hood??were do i start???

Ranger
04-27-08, 11:07 AM
Check the PCV line and cam cover grommet for starters. You may not hear it without a stethoscope. Spray some Brakleen around any suspect areas and listen for an RPM increase.

jrembold
07-30-08, 04:03 PM
I have a 2001 Catera 3.0 liter with the same code p0171 and p0174 which means both 1 and 2 banks are lean, however the car runs great, I've cleared the codes but the codes keep coming back, I have had a technician look at it and believes the injectors are clogged so they dissabled the fuel system and ran a cleaner solution through the system for $150.00 but the code came back in two days. the next move they say is to pull the injectors and rebuild or replace. Need help also?

Submariner409
07-30-08, 05:13 PM
speedydog, Start with ranger's PCV system checks then listen with a stethoscope (cheap at Walgreen, stick a piece of tubing on instead of the chest diaphragm.....) around the underside of the rubber connection (plenum) between the intake manifold and throttlebody, around the base of each intake runner, around the base of each fuel injector, and inside the end of the intake manifold just behind the p/s pump. A vacuum leak will be very hissy with the stethoscope.

jrembold, 99.99% of the time the fuel injectors have nothing to do with the lean codes. What I know about a Cat you can put on the point of a pin, but lean codes generally come from vacuum leaks. Speedydogs checks apply (in principle) to you, too.

Logandiagnostic
08-01-08, 01:09 AM
Their all going to do it sooner or later. Inspect the rubber coupler between the intake and the water crossover. $20 part.




Logan Diagnostic LLC
www.ledfix.com
www.airbagcrash.com
www.logandieselusa.com

landon101
08-01-08, 09:27 PM
it could be the plenum piece on the intake manifold or the intake seals
might have holes or cracks in them

i had these codes a few months back and thats what it was

atikovi
08-06-08, 09:16 PM
If you or your mech. had a smoke machine you could probably find the leak in 5 minutes.

codewize
08-07-08, 08:23 AM
if it's always consistantly bank 1 and only bank 1 then it's most likely NOT anything before the intake gaskets. A coupler or a plenum would inject air into both banks, not just one.

I've been battling this for a couple months myself. Next you'll start getting P0131.

RealmCenter
08-24-08, 11:48 AM
Watch for E85!! I had a 2006 S-Type come in for service that would flag P0171 and P0174 and pulled my hair out for days on it. It ran perfectly fine. Smoke tested it several times (totally tight). No audible vacuum leaks at all. When I would hard reset all the adaptions and watch the ECM switch into closed loop operation the short term fuel trims on both banks would shoot through the roof followed by the long terms. Everyone was stumped. We asked the customer over and over if he was using off brand gas or if this problem happened after a fill up. He swore he didn't (uh huh, right). Turned out it was E-85 in the tank which is much more oxygenated and a non flex fuel ECM determines this as a lack of fuel to maintain stoicheometric balance, tries to add fuel like crazy and trips lean codes. Funny thing is I decided to "experiment" with my supercharged GTP and put in E-85, ran perfectly fine, turned on the check engine light (as expected) but for some reason only picked bank 1 as lean (P0171). Just some food for thought. Good luck

codewize
08-24-08, 02:16 PM
Hmmm, Interesting. Suddenly my codes stopped. Interesting how I also switched back to Sunoco from Mobile.

v8motorcycleman
10-25-08, 10:40 AM
I have a 2001 Catera 3.0 liter with the same code p0171 and p0174 which means both 1 and 2 banks are lean, however the car runs great, I've cleared the codes but the codes keep coming back, I have had a technician look at it and believes the injectors are clogged so they dissabled the fuel system and ran a cleaner solution through the system for $150.00 but the code came back in two days. the next move they say is to pull the injectors and rebuild or replace. Need help also?

I had a '99 Catera I fought this exact issue for a few months. Turned out to be the Mass Air Flow Sensor. Iinstalled a new one and never had another code.

Submariner409
10-25-08, 12:02 PM
This thread and several others similar to it seem to surface every month or so, so I'll throw another bit of first-hand experience in the "Service Engine Soon" light and P017X lean code in the pot.

As many of you know, I have done quite a bit of experimentation with the stock DELPHI MAF and a JET Performance unit in my late '02 STS. A little over 5,000 miles worth to date..........It's a simple thing to change, so every now and then the urge to "try again" takes over and I stick the JET unit back in. Always the same result: decreased overall performance.

First off, no, the JET MAF is no miracle in a box. Quite the contrary. Because the JET is actually a stock DELPHI piece which has been mechanically (not electronically) altered, it upsets the upper rpm and WOT fuel/air ratios and periodically sets the SES and various lean codes. Second, there is a slight but measurable fuel mileage loss, on the order of .2 mpg. Third, there is a definite midrange throttle lag during acceleration and downshifts.

My take on the problem is that the various sensors interpret the increased upper rpm airflow (?) as a vacuum leak and then set fault codes. So many sensors are tied to proper A/F ratios in the later Northstars that it's impossible to change one value without simultaneously grooming the others to accept the change. In principle, the idea of increased performance due to more top end airflow is generally sound, BUT we're not dealing with a carbureted engine and we're not changing other system parameters to work with the airflow change.

Just some thoughts.......Good, sound Northstar PCM tuning is the answer. Absent that ability and there's no easy way to power.