# Cleaning the Mass Airflow Sensor (MAF) aka Hot wire modulator



## cjserio (Mar 18, 2008)

I just cleaned the MAF sensor on my 1994 4x4 2.4L truck and it solved most of my problems. It was very easy to do so i'm just writing this to let others know how they can do it.

If you're standing in front of the truck facing it with the hood open, the MAF sensor is on the LEFT side of the throttle body in the vacinity of the fuel filter. It's bolted to the throttle body using 3 machine screws.

Disconnect the plug, remove the 3 screws and it should come off very easily. BE CAREFUL taking it out. You don't want it to bang on the edges of the throttle body. Once you take it out, you'll notice 2 small wire coils that look sort of like the filaments of a light bulb. These are the "hot wires" that get the job done. I sprayed mine with electrical contact cleaner (which honestly just smelled like acetone) and then very very gently scraped it clean with a Q-tip. I have a stereo microscope that i used to be sure that i was cleaning it thoroughly.

Honestly, mine were not THAT dirty but a film was definitely visible as was some gunk on the top side (the side that faces the air cleaner). Once it was cleaned, i reinstalled it and my engine now has a totally different feel than it did before.

The symptoms that i had were a very powerless engine that was very slow to accelerate. Everytime i hit 3,000 RPM the engine felt like it could not rev up any hire and it started to buck. I'm sure the symptoms can vary across the board though since this is a major contributer in determining what the mixture is to the engine.

I hope this helps someone. Total time....30 mins.


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## paulsurfer (Aug 30, 2006)

I think cleaning the MAF sensor should be a regularly scheduled maintanence project for the HB.


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## 88pathoffroad (Jun 6, 2004)

Here's a link with pics, should be the same for the VG30i and Z24i with TBI.

How-to: Cleaning your MAF Sensor - Nissan Pathfinder Off-Road Association


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## patrick1963 (Feb 18, 2012)

cjserio said:


> If you're standing in front of the truck facing it with the hood open, the MAF sensor is on the LEFT side of the throttle body in the vicinity of the fuel filter. It's bolted to the throttle body using 3 machine screws.
> 
> Disconnect the plug, remove the 3 screws and it should come off very easily. BE CAREFUL taking it out. You don't want it to bang on the edges of the throttle body. Once you take it out, you'll notice 2 small wire coils that look sort of like the filaments of a light bulb. These are the "hot wires" that get the job done. I sprayed mine with electrical contact cleaner (which honestly just smelled like acetone) and then very very gently scraped it clean with a Q-tip. I have a stereo microscope that i used to be sure that i was cleaning it thoroughly.
> 
> I hope this helps someone. Total time....30 mins.


It helped me. Thanks!


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## jay5499 (Mar 13, 2012)

Yep i had the exact same issue with my 95. i used the actual mass air cleaner $7 and it did wonders. it had air filter fibers and black film on it. i also reset my ecu after i was done because it still had a slight hesitation then it went away completly. good piece of info.


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## TheRepairMan (Jun 30, 2009)

I'm glad to see this brought up again also. In another thread I had asked if "they" actually made a cleaner specifically for cleaning Mass Air Flow Sensors... and "they" do! It was CRC brand and I found it in an Advance Auto Parts store here for around $8.00. If that does anything close to being back into the correct range it's well worth that to even try. There may be other brands as well. We just need to keep in mind these sensors or "hot film" wires are very sensitive and fragile, but don't let that stop you from learning to do this service.

I'm just one of the many professional techs here on the Nissan board, and I've been cleaning throttle bodies for many, many years for minor drivability problems like poor idle and/or hesitation off idle, but this forum has made me rethink the service to include cleaning the MAF sensor with the throttle body cleaning.

So far, I have only cleaned a very few MAF's, and they were on turbocharged cars that were getting the sensor film oiled down, causing it to send incorrect air flow signals to the ECU, thus causing the fuel trim to reach its limits. That eventually sets a MIL on OBDII cars, but with many of our older vehicles, even non turbo models, often they can experience hot film contamination from normal events like crankcase ventilation vapor and intake reversion with no sign of a check engine light at all.

I believe this MAF contamination cause changes in the fuel mixture over time that leads to poor engine performance and efficiency. A careful cleaning of the MAF is a valid and plausible repair, and should become a part of our routine maintenance. Be sure to use the proper cleaning agent and method on your MAF sensor so not to cause other problems.

-Roger


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## jdg (Aug 27, 2009)

TheRepairMan said:


> I had asked if "they" actually made a cleaner specifically for cleaning Mass Air Flow Sensors... and "they" do! It was CRC brand and I found it in an Advance Auto Parts store here for around $8.00.


"MAF cleaner" specifically 'designed' for cleaning the MAF hot wire, has been around since at least 1990 (the first time I saw it), so likely it's been around for quite a bit longer.



> I believe this MAF contamination cause changes in the fuel mixture over time that leads to poor engine performance and efficiency.


If that were the case, why bother having O2 sensors in the exhaust stream to trim the mix?


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## TheRepairMan (Jun 30, 2009)

jdg said:


> "MAF cleaner" specifically 'designed' for cleaning the MAF hot wire, has been around since at least 1990 (the first time I saw it), so likely it's been around for quite a bit longer.
> 
> 
> If that were the case, why bother having O2 sensors in the exhaust stream to trim the mix?


You sure you don't mean Throttle Body Cleaner? The parts stores in my area just haven't had MAF sensor cleaner on the shelves. Not only that, but I've been to a ton of fuel system classes over the past decades and nobody EVER mentioned cleaning the MAF sensor. Throttle body and injectors, yes.

About the MAF versus O2 sensors... The MAF sensor can get so far out of range, thus make the engine run extremely rich, or lean, way beyond the point that the ECU can adjust the fuel trim no matter what the oxygen sensors are telling it. 

The primary sensors used by the ECU to help determine fuel injector duration, are the MAF, or MAP sensors, the TPS, the Coolant and Intake Air Temperature sensors. The upstream Oxygen sensors are only providing feedback to the ECU during closed loop conditions to keep the target fuel ratio around 14.7:1. The ECU can use O2 readings only to make smaller, short term fuel adjustments, known as "short term fuel trim", within a fairly small adjustment range. The range can change slightly over time, and this is known as "long term fuel trim"

I have seen MAF sensors get so bad, causing such a rich condition, that the spark plugs and oxygen sensors carbon foul beyond use.

-R


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