P0171 bank 1 too lean

[Isaac Montara]

I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.

I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.

But I don't know cars all that well.
How do I increase the idle RPM on an early 2000s Lancer ES?

[h***@ccanoemail.com]

On Thu, 27 Feb 2025 19:45:52 -0500, Isaac Montara

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.
I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.
But I don't know cars all that well.
How do I increase the idle RPM on an early 2000s Lancer ES?

How early ?
Why can't you state the year, model, engine, etc
Are your Japanese captors preventing your communications ?
Blink once for YES two for NO.
John T.

[Carol]

Post by h***@ccanoemail.com
On Thu, 27 Feb 2025 19:45:52 -0500, Isaac Montara

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps
coming back after I reset it with an OBDII hand-held code reading
tool.
I put new spark plugs in and it still sets the P0171 bank 1 too
lean. When it idles, it often kills the motor so it's not getting
enough fuel I think.
But I don't know cars all that well.
How do I increase the idle RPM on an early 2000s Lancer ES?

How early ?
Why can't you state the year, model, engine, etc
Are your Japanese captors preventing your communications ?
Blink once for YES two for NO.
John T.

Lol! I'm not at all a car person. All I come up with is old school.
Gunk in line (could have been stored wrong/too long with fuel gunking
up. Carb cleaner. The old stuff was in a can and had a plastic straw
you attached and sprayed in. Also there's stuff like STP/fuel cleaner
of some sort? Ok, laugh guys, that's my limit on this.

[retired1]

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.
I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.
But I don't know cars all that well. How do I increase the idle RPM on
an early 2000s Lancer ES?

Have you tried putting a fuel system cleaner in the gas tank, and then
driving the car for awhile to see if code stops ?

[AMuzi]

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that
keeps coming
back after I reset it with an OBDII hand-held code reading
tool.
I put new spark plugs in and it still sets the P0171 bank 1
too lean.
When it idles, it often kills the motor so it's not getting
enough fuel I
think.
But I don't know cars all that well. How do I increase the
idle RPM on an early 2000s Lancer ES?

This guy covered the usual items for 'lean bank'

PCM software needs to be updated
Vacuum leaks (Intake Manifold Gaskets, vacuum hoses, PCV
hoses, etc.)
Mass Airflow Sensor (MAF)
Plugged Fuel Filter or weak Fuel Pump
Plugged or dirty Fuel Injectors

without success but then discovered an unusual failure:

https://www.clublexus.com/forums/rx-2nd-gen-2004-2009/671879-finally-solved-p0171-and-p0174-codes.html

[Xeno]

Post by AMuzi

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.
I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.
But I don't know cars all that well. How do I increase the idle RPM on
an early 2000s Lancer ES?

This guy covered the usual items for 'lean bank'
PCM software needs to be updated
Vacuum leaks (Intake Manifold Gaskets, vacuum hoses, PCV hoses, etc.)
Mass Airflow Sensor (MAF)
Plugged Fuel Filter or weak Fuel Pump
Plugged or dirty Fuel Injectors
https://www.clublexus.com/forums/rx-2nd-gen-2004-2009/671879-finally-
solved-p0171-and-p0174-codes.html

Interesting story and there are many like this. But the dealer scan
tools should have been able to test for it. Look up OBD2 Mode $08 -
control operations of on-board systems. Mode $08 allows the tech to
control certain operations of the EMS allowing a scan tool to do
bidirectional control of an onboard system or test. Most solenoids and
emission equipment can be controlled and cycled independently of
conditions and commands. Factory scan tools and the more expensive
aftermarket scanners offer bi-directional functionality thus have Mode
$08 capabilities. This is a very handy method of testing for equipment
failure without the need to wait for the EMS to command the operation.
Would have been very handy for you, no need to wait out the time or an
idle situation.

HTH

[Xeno]

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.
I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.
But I don't know cars all that well. How do I increase the idle RPM on
an early 2000s Lancer ES?

If you have a definite P0171 DTC, then best you determine why Bank 1 is
being deemed too lean. The DTC alone is providing insufficient data -
it's a diagnostic starting point, nothing more. An intake system air
leak can cause such an issue so look at the intake system carefully for
cracked hoses and/or loose hoses or ducting. So can partially blocked
injectors. Take a look at LTFT and STFT data. Look at live data, look at
freeze frame PIDs. A 20+ year old car is likely to have perished hoses
and ducting and can be a PITA to locate when they become the cause of
air leaks.

If you aren't familiar with OBD2 data, consult someone who is. You need
to know what data is *normal* and what data is *within spec*

Dicking with the idle speed *will not fix the issue*. The idle speed is
merely a symptom of idle air enleanment, not the cause.

[Scott Dorsey]

Post by Isaac Montara
I have a Mitsubishi Lancer ES early 2000s with a P0171 that keeps coming
back after I reset it with an OBDII hand-held code reading tool.
I put new spark plugs in and it still sets the P0171 bank 1 too lean.
When it idles, it often kills the motor so it's not getting enough fuel I
think.

Why plugs? That's not likely to be related in any way, it is not like you
are getting a spark error.

Your first job is to figure out if it really IS too lean or if the computer
is deluded.

You need a real scan tool so you can see if the other bank is being
forced too rich or not.

With an inline engine where everything is one bank you can smell the
exhaust and tell if it's too rich or too lean, but you're going to need
the proper tool for this one.

Post by Isaac Montara
How do I increase the idle RPM on an early 2000s Lancer ES?

Why would you want to increase the idle RPM? If the engine really IS
running too lean, that's a good way to burn some valves. On the other
hand if the engine is running rich and the computer thinks it's too
lean, that also does nothing to help the problem.
--scott