# P0171, P0131, and P0137 codes



## JLL (Sep 12, 2017)

Read these if you have the turbocharged 1.4L. These engines are very sensitive to even the smallest vacuum leak. 









2011-2016 Cruze Limited 1.4L PCV System Explained


2011-2016 Cruze Limited 1.4L PCV System Explained Video: I made a video to help better explain how this whole PCV system works to supplement this article. Overview: The purpose of this post is to explain the function of the PCV system in the 1.4L Turbo engine so those of you who are having...




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2011-2016 Cruze 1.4 PCV Valve Cover/Intake Manifold Issues


I'm not asking about the check valve in the intake manifold. I'm asking about the PCV diaphragm in the valve cover. Sorry, I did not see that you were asking about the regulator.




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## otacon122 (Sep 2, 2015)

JLL said:


> Read these if you have the turbocharged 1.4L. These engines are very sensitive to even the smallest vacuum leak.
> 
> 
> 
> ...


I have the 1.8L LUW "Flex Fuel" engine. Also, can it really take E85?

By the way, for those who are wondering, the difference between the LUW and LWE designations is the LUW is the flex fuel engine while the LWE is not. Otherwise the engines are identical.


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## JLL (Sep 12, 2017)

A flex fuel engine can run E85


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## otacon122 (Sep 2, 2015)

JLL said:


> A flex fuel engine can run E85


Update: Long-Term Fuel Trim at 1500rpms (45mph cruise) stays between 0 and +5.


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## JLL (Sep 12, 2017)

otacon122 said:


> Update: Long-Term Fuel Trim at 1500rpms (45mph cruise) stays between 0 and +5.


That's normal. What are the STFTs?


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## otacon122 (Sep 2, 2015)

JLL said:


> That's normal. What are the STFTs?


STFT jumps between -5 and +10 at 1500rpms. At idle, it spikes into the +20's and +30s and the LTFT quickly follows.


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## JLL (Sep 12, 2017)

Sounds like you might have a vacuum leak. I would do a pressurized smoke test to locate it.


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## otacon122 (Sep 2, 2015)

JLL said:


> Sounds like you might have a vacuum leak. I would do a pressurized smoke test to locate it.


I figured that's what it was. I checked the EVAP canister and it doesn't pull air when commanded off, so I'm assuming the PCV thing is a problem on the 1.8L engines, too?


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## otacon122 (Sep 2, 2015)

JLL said:


> Sounds like you might have a vacuum leak. I would do a pressurized smoke test to locate it.


Also, GM service manual says desired fuel pressure should be 44.5psi but I'm getting 57 or 58 psi. Is that normal? If it helps, I put about 9.6 gallons of the "unleaded 88" fuel into the car, which is supposed to be the 15% ethanol blend, mixed with about 6 gallons of 87 octane non-ethanol fuel. Car has run on non-ethanol fuel most of its life.


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## Blasirl (Mar 31, 2015)

*2011-2016 1.8L PCV, Valve Cover, issues*


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## otacon122 (Sep 2, 2015)

Blasirl said:


> *2011-2016 1.8L PCV, Valve Cover, issues*


Update: Attempting to maintain 30mph and 1500rpms up a hill with 35% throttle, STFT was between -5 and -20 while LTFT was between +5 and +15. Full throttle, both numbers run right about zero, give or take.

Mass air flow sensor shows 0.23lb/min at idle and 0.64lb/min when driving at normal city speeds. That comes out to 1.78g/second at idle and 4.83g/sec when driving.

What is considered normal for MAF sensor readings?


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## JLL (Sep 12, 2017)

otacon122 said:


> Also, GM service manual says desired fuel pressure should be 44.5psi but I'm getting 57 or 58 psi. Is that normal? If it helps, I put about 9.6 gallons of the "unleaded 88" fuel into the car, which is supposed to be the 15% ethanol blend, mixed with about 6 gallons of 87 octane non-ethanol fuel. Car has run on non-ethanol fuel most of its life.


You can try resetting the fuel trims for the 15% ethanol content. Disconnect the negative battery cable for awhile. In most areas of the country "regular" gasoline has 10% ethanol in it.

This is what my service manual says about fuel pressure:

Key on, engine off: 50 to 94 psi
Engine idling: 43 to 58 psi


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## otacon122 (Sep 2, 2015)

JLL said:


> You can try resetting the fuel trims for the 15% ethanol content. Disconnect the negative battery cable for awhile. In most areas of the country "regular" gasoline has 10% ethanol in it.
> 
> This is what my service manual says about fuel pressure:
> 
> ...


I'm going to clean the MAF sensor and throttle body on my car, then if that doesn't fix the problem, I will replace the valve cover. When it comes time to refuel, I will refuel with E15, drive home, then pop the battery, give it about 10 minutes, then start it up and drive it around then I will post the readings for E15 on a stock 1.8L.


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## JLL (Sep 12, 2017)

otacon122 said:


> I'm going to clean the MAF sensor and throttle body on my car, then if that doesn't fix the problem, I will replace the valve cover. When it comes time to refuel, I will refuel with E15, drive home, then pop the battery, give it about 10 minutes, then start it up and drive it around then I will post the readings for E15 on a stock 1.8L.


There have been a few posts on cleaning the throttle body lately. As a warning, DO NOT open and closed the throttle plate manually while cleaning it. Many people have broken the internals of the throttle body that way.


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## otacon122 (Sep 2, 2015)

JLL said:


> There have been a few posts on cleaning the throttle body lately. As a warning, DO NOT open and closed the throttle plate manually while cleaning it. Many people have broken the internals of the throttle body that way.


MAF sensor currently reads 0.23lb/minute at idle and 0.46lb/minute at a 1500rpm cruise. What should they be?


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## JLL (Sep 12, 2017)

otacon122 said:


> MAF sensor currently reads 0.23lb/minute at idle and 0.46lb/minute at a 1500rpm cruise. What should they be?


It's not really a matter of: "What should that be?" It's more a matter of: Does the MAF reading match up with the air speed density calculation made by the ECM.

If you think you have a vacuum leak, perform a smoke test. If you have a leak, a smoke test will not only tell you that there's a leak, it will tell you where the leak is!


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## otacon122 (Sep 2, 2015)

JLL said:


> It's not really a matter of: "What should that be?" It's more a matter of: Does the MAF reading match up with the air speed density calculation made by the ECM.
> 
> If you think you have a vacuum leak, perform a smoke test. If you have a leak, a smoke test will not only tell you that there's a leak, it will tell you where the leak is!


MAP sensor is showing 13 inches of mercury while the barometric pressure sensor is showing 29 inches of mercury. Airport reads 30.32 inches. Intake air temperature is nearly 20 degrees warmer than ambient.


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## JLL (Sep 12, 2017)

otacon122 said:


> MAP sensor is showing 13 inches of mercury while the barometric pressure sensor is showing 29 inches of mercury. Airport reads 30.32 inches. Intake air temperature is nearly 30 degrees warmer than ambient.


You don't really understand what your looking at, do you?

The numbers can only tell you so much about what's going on. At some point you actually need to do some actually testing.

You might be better off taking you car to a shop to have a technician look at it.


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## otacon122 (Sep 2, 2015)

JLL said:


> You don't really understand what your looking at, do you?
> 
> The numbers can only tell you so much about what's going on. At some point you actually need to do some actually testing.
> 
> You might be better off taking you car to a shop to have a technician look at it.


Ho, boy. Well, this helps me narrow down the problem. The car will just randomly drop into limp home mode while I am driving. Interestingly it doesn't throw any CEL codes except P0171. I noticed that at almost the exact instant the car dropped into Limp Home mode, the Mass Air Flow sensor reading spiked to more than 1.2lbs/minute but the RPMs did not go above 2k rpms at that point. Spark retard was almost 25 degrees. There was a point in the limp home mode drive back home where the RPMs hit 3k and the Mass Air Flow sensor showed 1.5lbs/minute. If I park it, turn it off, and let it sit for a few minutes, it comes back out of Limp Home mode on its own.

Good thing I have a bottle of Mass Air Flow sensor cleaner waiting.


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## otacon122 (Sep 2, 2015)

JLL said:


> You don't really understand what your looking at, do you?
> 
> The numbers can only tell you so much about what's going on. At some point you actually need to do some actually testing.
> 
> You might be better off taking you car to a shop to have a technician look at it.


Great news! Cleaning the Mass Air Flow sensor seems to have solved the problem. Short Term Fuel Trim at idle is now consistent between +2 and -3.5 and long term fuel trim hovers between +19.5 and +20.5. Mass Air Flow sensor is now reading 0.55lb/minute at idle as well. And this is before popping the battery to remap.


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