Car running too lean code p0171 an p0174
11-17-2009, 02:15 AM
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Car running too lean code p0171 an p0174 Hello iam new to this site so iam not sure if this belongs here.Ive been having problems with my car running too lean after having my computer tuned(got the power tune,deleted the egr sys,an the air pump).at first i thought it was the o2 sensors but after i exchanged them it was still the same.i also checked the fuel pressure an was at 58psi,checked for leaks their wasnt any an even tried 2 different mass air flow sensors an still the ses light was on.my car pretty much a stocker ecxept for the lid,85mm slp mass air flow,and LT headers.ur input is very welcome
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11-25-2009, 07:36 PM
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car pretty much a stocker except for the lid,85mm slp mass air flow,and LT headers.ur input is very welcome
11-26-2009, 12:05 AM
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just went through diagnosing a car with the same code.
in your case
A vacuum leak. check the manifold sealing gaskets and check the rear map sensor o ring and vacuum hose and or power booster hose
it could be a leak in the exhaust manifold before it reaches the o2 sensor.
it can also be a clogged fuel filter as well. even tho the pressure is fine the flow can be weak.
in your case
A vacuum leak. check the manifold sealing gaskets and check the rear map sensor o ring and vacuum hose and or power booster hose
it could be a leak in the exhaust manifold before it reaches the o2 sensor.
it can also be a clogged fuel filter as well. even tho the pressure is fine the flow can be weak.
11-26-2009, 10:07 AM
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It may well be your fuel filter. My 1999 Z28 was giving me the blues until I figured to change what I hadnt since I had the car.
Does your car only give this code after higher rpm driving? Mine was like that, would not throw the code until revved, it will idle & drive normal all day.
See O2 sensors translate info to the computer, computer sees a weakness & triggers that the engine has run lean, they(O2 sensor) dont -make- it run lean. And like buddy said, you may have 58 psi @ idle because there is no demand for flow.
And what kind of tune was this?
Was it supposed t oremap fuel delivery?
Simple parts get over looked. Good luck. Besides, its a good measure to keep that pump healthy. A clogged filter is like too much regulation.
Does your car only give this code after higher rpm driving? Mine was like that, would not throw the code until revved, it will idle & drive normal all day.
See O2 sensors translate info to the computer, computer sees a weakness & triggers that the engine has run lean, they(O2 sensor) dont -make- it run lean. And like buddy said, you may have 58 psi @ idle because there is no demand for flow.
And what kind of tune was this?
Was it supposed t oremap fuel delivery?
Simple parts get over looked. Good luck. Besides, its a good measure to keep that pump healthy. A clogged filter is like too much regulation.
12-22-2012, 04:00 PM
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P 171 - 174 codes. This might help those with LS1 Gen 3 engines with lean codes P 171 / 174
The most common fault that I have come across here in Australia for this code is a vaccum leak on standard non modified engines & can be checked as follows:
1. check the PVC line, don't just look at it, physically check it by lightly tugging on it or physically remove it & check it, 85% of the time you will find the rubber section melted underneath because of the heat output of the Aluminum Engine. In most cases when this is found damaged & replaced it will solve the problem.
For those not familar with the PVC line its the line that connects to the intake manofold just behind the thottle body & runs down RHS side of the engine around the back of the manofold to the rear of the LHS rocker cover when looking from behind the engine. It also has a earth wire connect to the water transfer pipe on front of the engine.
You can also check the manofold bolts to make sure they haven't become lose because of the heat that allows the bolts to slowly stretch over time.
Also check the rubber hoses that are connect to the back of the inlet manofold.
Check to see the inlet section from the aircleaner box to thottle body isn't damaged. If it is replace it, this will give the MAF sensor a false reading.
2. check the fuel pressure by a guage connected to the fuel rail with enough hose to run into the cabin area of the car, take it for a drive if the pressure drops from 4 bar or 58 PSI & keeps dropping then change the fuel filter, After changing that take for another drive if the same problem occurs then chances are the fuel pump requires replacing
3. If you have hadn't had your Injectors cleaned before then have them done professionally, It takes them about 30 minutes to be done & if they were dirty you should see an improvement in thottle response. Injector cleaner via the fuel tank is a waste of time and money in my view.
4. Check the High Voltage spark leads, Start the engine with emergency brake on & the gear box in netural or park, place a sheet of black darkening plastic over the hood, wait for your eyes to adjust to the darkness under the pastic, look to see if your leads are arcing on the outside. If they are turn the engine off and change them. Also check your spark plugs while you are at it, if the centre electrode of the plug is worn or melted because of the leaning of the engine then replace them as well. Warning don't touch the spark plugs leads ever whilst the engine is running.
5. Generally changing the O2 sensors will not do anything, if these fail they will generally give a different code
The most common fault that I have come across here in Australia for this code is a vaccum leak on standard non modified engines & can be checked as follows:
1. check the PVC line, don't just look at it, physically check it by lightly tugging on it or physically remove it & check it, 85% of the time you will find the rubber section melted underneath because of the heat output of the Aluminum Engine. In most cases when this is found damaged & replaced it will solve the problem.
For those not familar with the PVC line its the line that connects to the intake manofold just behind the thottle body & runs down RHS side of the engine around the back of the manofold to the rear of the LHS rocker cover when looking from behind the engine. It also has a earth wire connect to the water transfer pipe on front of the engine.
You can also check the manofold bolts to make sure they haven't become lose because of the heat that allows the bolts to slowly stretch over time.
Also check the rubber hoses that are connect to the back of the inlet manofold.
Check to see the inlet section from the aircleaner box to thottle body isn't damaged. If it is replace it, this will give the MAF sensor a false reading.
2. check the fuel pressure by a guage connected to the fuel rail with enough hose to run into the cabin area of the car, take it for a drive if the pressure drops from 4 bar or 58 PSI & keeps dropping then change the fuel filter, After changing that take for another drive if the same problem occurs then chances are the fuel pump requires replacing
3. If you have hadn't had your Injectors cleaned before then have them done professionally, It takes them about 30 minutes to be done & if they were dirty you should see an improvement in thottle response. Injector cleaner via the fuel tank is a waste of time and money in my view.
4. Check the High Voltage spark leads, Start the engine with emergency brake on & the gear box in netural or park, place a sheet of black darkening plastic over the hood, wait for your eyes to adjust to the darkness under the pastic, look to see if your leads are arcing on the outside. If they are turn the engine off and change them. Also check your spark plugs while you are at it, if the centre electrode of the plug is worn or melted because of the leaning of the engine then replace them as well. Warning don't touch the spark plugs leads ever whilst the engine is running.
5. Generally changing the O2 sensors will not do anything, if these fail they will generally give a different code
Last edited by RR 474; 12-22-2012 at 04:32 PM.
