help! Too lean!
Thread Starter
Launching!
Joined: Oct 2002
Posts: 286
Likes: 0
From: OHIO
help! Too lean! Have been getting SES light on and off so I had it scanned and got codes 171 and 174 which are too lean bank one and bank two! Anyone know what could cause it or maybe how to fix it? Any help will be great! THANKS! 
On The Tree
Joined: May 2003
Posts: 106
Likes: 1
From: Apache Junc, Az
Re: help! Too lean! In the fuel system it could be a bad fuel pressure regulator, low fuel pressure of a bad injector or injector circuit. First thing I would do is replace the fuel filter, that's a very good possibility..
You could have a vacuum leak in a vacuum line, PCV system or even an oil dipstick or loose oil cap could do it. You could also have an EGR valve not closing completely.
The MAF sensor might be contaminated. When a MAF sensor gets contaminated it skews the transfer function such that the sensor over-estimates air flow at idle and causes the fuel system to go rich. It also under-estimates air flow at high air flows and causes fuel system to go lean. This means Long Term Fuel Trims will learn lean (-) corrections at idle and learn rich (+) corrections at higher air flows. I have heard of people spraying electrical cleaner on the MAF elements and solving this problem but would not recommend it unless you are positive it is the MAF. (nothing to loose).
You could have a vacuum leak in a vacuum line, PCV system or even an oil dipstick or loose oil cap could do it. You could also have an EGR valve not closing completely.
The MAF sensor might be contaminated. When a MAF sensor gets contaminated it skews the transfer function such that the sensor over-estimates air flow at idle and causes the fuel system to go rich. It also under-estimates air flow at high air flows and causes fuel system to go lean. This means Long Term Fuel Trims will learn lean (-) corrections at idle and learn rich (+) corrections at higher air flows. I have heard of people spraying electrical cleaner on the MAF elements and solving this problem but would not recommend it unless you are positive it is the MAF. (nothing to loose).
Thread Starter
Launching!
Joined: Oct 2002
Posts: 286
Likes: 0
From: OHIO
Re: help! Too lean! MAF IS ONLY A FEW MONTHS OLD, MABE 1000 MILES ON IT ANY PLACE I SHOULD START, GUESS I WILL REPLACE THE FUEL FILTER AND START THERE. THANKS ALOT FOR AN IDEA ON WHERE TO START!
On The Tree
Joined: May 2003
Posts: 106
Likes: 1
From: Apache Junc, Az
Re: help! Too lean! Try a couple of things before you take it in. These are common things that are normal maintenance that should be done anyway, so start here.
You replaced the fuel filter -done
Replace the PCV valve
Inspect each vacuum line for leaks/cracks
Clean the air cleaner
Reseat the oil dip stick
Reseat the oil cap
Check the gas cap
Run a bottle of fuel injector cleaner
Check the EGR valve
With the engine running, place your fingers under the EGR valve and goose the engine. The pintle should move up rapidly and come right down. If it doesn't move, then there is a problem with the EGR. If it does, then the EGR valve and the EGR system are okay. Now take the vacuum line off the EGR valve and, with a hand operated vacuum pump, slowly apply vacuum to the EGR valve. The engine should start to stumble and eventually die out if the valve is operating correctly.
You replaced the fuel filter -done
Replace the PCV valve
Inspect each vacuum line for leaks/cracks
Clean the air cleaner
Reseat the oil dip stick
Reseat the oil cap
Check the gas cap
Run a bottle of fuel injector cleaner
Check the EGR valve
With the engine running, place your fingers under the EGR valve and goose the engine. The pintle should move up rapidly and come right down. If it doesn't move, then there is a problem with the EGR. If it does, then the EGR valve and the EGR system are okay. Now take the vacuum line off the EGR valve and, with a hand operated vacuum pump, slowly apply vacuum to the EGR valve. The engine should start to stumble and eventually die out if the valve is operating correctly.
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TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
Re: help! Too lean! Put the stock MAF back in, That SLP is causing unmetered airflow and unless you tuned the PCM or increased injector flow the problem will not go away in the summer weather, plus as the weather gets hotter so does the intake air temps and will only get leaner and induce knock with loss of timing.
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Re: help! Too lean! team zr-1 though what you say is a possibility i think you are jumping to conclusions ive heard much good about the slp 85mm units in fact i use one my self and currently have no problems after about 6000-7000 miles of use im no expert but the slp units usally only cause knock at wot if any thing id look at possibly a bad 02 sim or a clogged filter or a cloged injector, or seeing that your runnig nos it could also be you messed up your maf sensor (that is if you are uning a wet shot) theres many things the first thing id do is reset your pcm and see if the comp learns the maf if not id remove is since its the easyest to check and reset pcm and see if you fix who knows !!! just take your time and dont jump to conclusions good luck!
TECH Apprentice
Joined: Jan 2002
Posts: 337
Likes: 0
From: O'Fallon-MO.
Re: help! Too lean! To pull those lean codes like that you have to have a leak somewhere.Your pullin both codes which is both banks so its either the whole intake or somewhere between the MAF and the intake leaking.And check your EGR tube going into the intake. I was fighting the same problem for almost a year and could never figure it out.It always pulled those codes, but on the dyno I wideband the car and it was running rich so I found out it was pullin those codes from idling and my LTrims were maked out +25 lean.
Come to find out,a year later I found out it was my BRAND NEW ls6 intake leaking from a piece that goes into the back of the intake for the brake booster hose.
Good luck in finded your leak.
Come to find out,a year later I found out it was my BRAND NEW ls6 intake leaking from a piece that goes into the back of the intake for the brake booster hose.
Good luck in finded your leak.
Re: help! Too lean! SLP MAF comes in two flavors, one for '01-'02
and one for '98-'00. Mine works perfectly ('01-'02
MAF, '02 car). But, from what I gather, the
'98-'99 years and '00 were not set up the same,
mixture-target-wise (and '98 PCM is different
from all others) so this early-years, one-size-
fits all MAF may not be cal'd to the ideal tune
for all of the models it purports to cover (or,
what SLP does to make a '98 happy may annoy a
'00). One size fits all, still fits some better
than others.
So the idea of swapping back the stock MAF as a
diagnostic "cut" is certainly sensible, and if
it results in better performance, leave it on.
and one for '98-'00. Mine works perfectly ('01-'02
MAF, '02 car). But, from what I gather, the
'98-'99 years and '00 were not set up the same,
mixture-target-wise (and '98 PCM is different
from all others) so this early-years, one-size-
fits all MAF may not be cal'd to the ideal tune
for all of the models it purports to cover (or,
what SLP does to make a '98 happy may annoy a
'00). One size fits all, still fits some better
than others.
So the idea of swapping back the stock MAF as a
diagnostic "cut" is certainly sensible, and if
it results in better performance, leave it on.
Re: help! Too lean! After 4 years of playing with the MAF, I'm coming ot the same conclusion. I may even get a hold of a stock MAF with the screen again. I've tried GMAF, stock screenless and PACE VV. Ultimately ( like after 500-1000 miles testing ) I go back to stock. Maybe with LS1Edit dyno wide band tuning I'll find different answers, but for now, stock runs the best.
