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Discussion Starter #1
So my 2012 3SA (MT) has been running great. It started up and ran great this morning. After work today, it started and instantly stalled. Started again, instantly stalled.

So, I gave it some gas, and it ran, but a little rough. If I feathered the pedal, it would run pretty nice at 3k and up to redline.
Below 3k, it would surge between 500 and 2.5k. Release the throttle and instant stall.

When I'm holding the throttle down to 3k RPM, the exhaust smells really rich.

Checked engine codes:
P0172 - System Too Rich Bank 1
P0101 - Mass Air Flow Sensor Circuit Range/Performance problem

Cleaned the MAF sensor with spray. Let it dry. Cleaned it again (as well as I can.. I'm used to seeing the sensor wire, but this one has a little tunnel where I assume the wire is). Let it dry. Reinstalled.

Started the car, instant stall.

I pulled the MAP sensor and it was covered in oil. Cleaned, dried, cleaned, dried, reinstalled.

Started the car, instant stall.

Removed negative battery terminal. Pressed the brake pedal five times. Replaced negative battery terminal.

Started the car, instant stall.

At this point I limped it home and it's in the driveway. While driving home, if the rpm was above 3k, it drove pretty much normal. Shifting was interesting due to it wanting to stall instantly.

The oil on the MAP sensor has me concerned a bit... Doesn't seem like it should be oily, but what do I know?

The P0172 code could also be a fuel injector leaking fuel into the cylinder or a faulty fuel pressure regulator (pressure too high? too low?)
(among many other things)...


Any ideas of what I should try next? New MAF? New MAP? Test the fuel pressure? Pull the injectors and do a leak down test?
 

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I'd say the problem stems from the P0101 code. If the MAF is sending the PCM the wrong information (its not working right) then the PCM will not meter the fuel properly. The car runs ok above 3k rpm, thats probably within the range of fuel delivery according to the signal from the MAF. Below 3k rpm the MAF may still be calling for fuel appropriate for above 3k rpm, so its just dumping fuel, thats why the P0172 code. Check the fuel pressure and if you can check the output range of the MAF signal against the normal range.
 

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Discussion Starter #3
Any idea what the normal range is?

I was looking at the MAP sensor because I have a Silverado and it was throwing a MAF error, even with a brand new Bosch MAF filter. Then I cleaned the MAP sensor and the MAF error code went away.
 

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Discussion Starter #4
More Codes!

Bah.... Today I pulled the MAF to test it. Even with zero airflow, it was reading over 100 CFM... When I blew in it, it went up as expected. The service manual simply says to see if it varies when you blow air through it.

Another thing that I forgot to mention above is that something is buzzing in the engine compartment even with the engine off. I believe that I've narrowed it down to the Throttle Position Sensor. I disconnected it and the buzzing stopped. I plugged it back in and it didn't return until after I started the engine once. Then the buzzing came back. During that initial start, the throttle pedal did nothing at all. Pressing it down and the engine stayed at rough idle.

The car actually started and just did some searching in the RPMs, around 1.5-2k I think.

I pulled the codes and it's gotten uglier!

Current Fault Log
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P0223: Throttle/Pedal Position Sensor/Switch "B" Circuit High Input
P061B: null

Pending Fault Log
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P0113: Intake Air Temperature Circuit High Input
P0123: Throttle/Pedal Position Sensor/Switch A Circuit High Input
P0222: Throttle/Pedal Position Sensor/Switch "B" Circuit Low Input

Historic Fault Log
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P0101: Mass or Volume Air Flow Circuit Range/Performance Problem
P0102: Mass or Volume Air Flow Circuit Low Input
P0172: System too Rich (Bank 1)
Other discovered fault codes
(possibly pending, current or manufacturer specific)
----------------------------------------------------
ECU reports no other fault codes logged

End of report.
 

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Discussion Starter #5
I bought a new MAF sensor from Amazon for about $70 and that fixed the car right up. Well, installing the new sensor did the job.
 
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