Lexus GS (1998-2005) GS 400 & GS 430 Mass Air Flow Sensor Cleaning DIY

Clean the Mass Air Flow Sensor (MAF) on a 1998-2000 Lexus GS 400 or a 2001-2005 Lexus GS 430

Works For:
1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Lexus GS 400 & GS 430 Models

Source: ClubLexus

Why: to remove deposits on the MAF sensor, and carbon deposits on the throttle body that rob the car of fuel economy, power, throttle response, and idle smoothness
Cost: $10 in parts [CRC MAF cleaner ($6) and Valvoline Carb, Choke, & Throttle body cleaner ($4)] Time: 30-45 minutes
Difficulty rating:2 of 5 (pretty easy to do)
How often: recommend once every 2 years (or when you replace your air filter)
Result: smoother idle while in gear and parked, better fuel economy, and more immediate, instant throttle response.

Material/Parts used:
1. CRC Masss Air Flow Sensor Cleaner [$6 from Schuck’s] 2. Valvoline SynPower Carb, Choke, and Throttle Body cleaner [$4 from Schuck’s] 3. 8mm and 10mm sockets with 3” extension
4. Needle nose pliers (to slide hose clamps)
5. Nitrile gloves (to keep your hands clean)
6. Clean cotton shop towels
7. RECOMMENDED: new air filter (while you’re there, why not change it as well)


1. MAF sensor cleaning. Very easy.
a. Start by unclipping the wiring harness to the MAF sensor on top of the air filter housing. Note: you do NOT need to remove the whole air filter housing from the car.
b. Next, remove the 2 bolts that hold the MAF sensor to the top of the air filter housing.
c. Gently pull out the comet shaped MAF sensor (a rubber O-ring will come off with it, so be careful not to lose it). One end is open (points towards the air filter) and has a protective plastic square mesh, and if you look deep, you’ll see the sensor wires–that’s what you’ll need to clean.

To clean the MAF, I used the following brand of MAF-specific cleaner:

CRC Masss Air Flow Sensor Cleaner

It’s supposed to be VERY gentle for electronics, does not harm plastics, and quickly evaporates. I would highly suggest that you only use cleaners specifically made for the purpose of cleaning MAF sensors, as other engine cleaners may damage your very delicate MAF sensor–just spend the time and money on getting the right product from the start.

As a side note, prior to cleaning, the MAF sensor elements APPEARED clean. Nonetheless, with the MAF pointed somewhat upwards for proper draining (open end pointed downwards), I did about 20 quick pulse sprays with the nozzle pointed towards the 2-3 metal elements and let the cleaner drain out. Do NOT directly touch the metal sensors within the MAF as you may break them. Gently roll your MAF in different directions to get all of the cleaner out of the sensor. My MAF sensor was a bit shinier after the cleaning process with MAF cleaner.

Replace the MAF back onto your air filter housing, secure with the 2 bolts, and reconnect the wire harness. You’re done with the MAF sensor cleaning.

A schematic of how the MAF sensor is mounted on the air filter box. Alternatively, if you didn’t want to take out the MAF sensor, you could take off the top part of the air filter box (i.e. disconnect it from the “intake air connector pipe”) and just spray clean the MAF while it’s attached to the housing–however, it’s a bit harder to see the metal MAF sensor elements you need to clean and might not get optimal results.

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