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Aug 31, 2023

MAF Testing : Nissan Skyline GT-R Mass air flow sensor

We have/use a lot of MAF or mass air flow meters for Nissan Skyline GT-R. 

Old cars. You will probably see me write that 100, 1000 times on here and to people. Obviously nothing is forever. In the terms of vehicle electronic components that live under hood, and are subjected to years of vibration, and heat, they can and will break.   The Nissan RB mass airflow sensor is a great device, and is given a bad rep by people that don't understand how it works, and why it is a superior system to measure an engines requirements in many cases(not all).

Bad connections, bad solder joints, blow off valves to atmosphere, and leaks can all cause issues.  What seems like a 2500 rpm limiter, is often a bad/failing sensor. Stalling when you let off the throttle is normally a BOV to atmosphere.  The R35, or later Nissan blade style sensor is superior to this era of Nissan MAF, but its not a simple plug and play. It requires a housing, wiring, ECU tune to support the later MAF. 

Since we have a lot of MAF, I had to see if I could sort a good RB26 MAF from a bad one

The mass airflow sensor (MAF sensor) is a critical component in the fuel injection system of the Nissan Skyline GT-R. It measures the mass of air flowing into the engine, which is then used by the engine control unit (ECU) to calculate the correct air-fuel ratio for combustion.

The dual MAF sensors are located before each turbo, and  consist of a heated wire or hot film element that is exposed to the airstream. As the air flows past the element, it cools the element, and the ECU measures the amount of current required to keep the element at a constant temperature. This current measurement is then converted into a mass airflow reading. As you can see in the video below, an RB26 will actually run on no MAF. It even will take throttle. I don't recommend driving one like this, but if you suspect issues, unplugging both MAF may allow you to limp home. 

They often fail because internally the connector into the OEM board solder joint cracks. This creates an odd or failed reading. Normally just reflowing the solder joint can fix it. 

Testing a MAF

I made a little rig with a Milwaukee 12v battery, some Anderson plugs, and a Fluke multimeter. It seems that when the output voltage settles above about 0.16 v with no movement, then the MAF runs good on a car. When it drops lower than that, the MAF does not work in most cars we have tested.  

This MAF seems to test OK. I do hate when someone uses the orange OEM Nissan silicone to seal a MAF. 

I also use an ECUtalk to look into the MAF. Here you can see the front MAF is 1.2 volts, and the rear 0.8 volts. Its pretty normal to have a split up to about 0.5 volts. Closer together would be in theory better, but with different intake and exhaust tracts, this is what we see. 

A bad MAF sensor can cause a variety of problems with a Skyline GT-R, including:

Engine hesitation or stalling
Rough idle
Poor fuel economy
Increased emissions
Check engine light

Here are some of the symptoms of a bad MAF sensor in a Nissan Skyline GT-R:

Engine hesitation or stalling
Rough idle
Poor fuel economy
Increased emissions
Check engine light
Engine surging
Engine knocking
Loss of power

If you experience any of these symptoms, it is important to have your MAF sensor checked by a qualified technician as soon as possible. A bad MAF sensor can cause a number of other problems with your Skyline GT-R, so it is important to have it replaced as soon as possible.

The MAF sensor is a relatively inexpensive part, and it is relatively easy to replace. 

Here are some tips for preventing MAF sensor problems in your Nissan Skyline GT-R:

Keep the air intake system clean and free of debris.
Avoid driving through deep water or puddles.
Have the MAF sensor cleaned or replaced regularly, as recommended by the manufacturer.
By following these tips, you can help to keep your MAF sensor in good condition and prevent problems.

OEM MAF metering ranges

------ --------- OD mm--- RWHP ---- RWHP ---- BHP ------ BHP
No of AFM's ---- -------- 1 ---------- 2 ------------- 1 -------- 2
RB26 ---------- 65 ------- 200 ------ 400 ------- 271 ------ 474
RB20/25 ------ 80 ------- 300 ------ 600 ------- 376 ------ 683
Z32 ------------- 8075---- 340 ----- 685 ------- 415 ------ 763
Q45 ------------ 90 ------- 400 ------ 810 ------- 479 ------ 890

R35/Nissan   70  ----- 300---------600
R35/Nissan   76.5-----350 --------700
R35/Nissan   88.9-----500--------1000

PMAS HPX   63.5----580 -----   1160
PMAS HPX   70 -----640------- 1280
PMAS HPX   76.5 ---830 -----  1660
PMAS HPX   88.9 ---1130 ------2260

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