MAF Sensor and Throttle Body Cleaning DIY: GS400 & GS430

[SeattleGS400]

I have a 99 GS400, and I had a slightly rough idle when parked in gear and I thought my engine and/or transmission mounts might be wearing out--not the case at all. Nonetheless, after some research, as the MAF sensor calculates how much volume of air and oxygen is getting into the car, I thought my car might be running a bit off (probably too "rich" (i.e. too much fuel injected) running, as my gas mileage was a bit down), so I attempted cleaning the MAF. The MAF sensor can get dirty over time with microscopic debris, oil, air filter fibers, dust and pollen, so an occassional cleaning is warranted. Next, I also read that cleaning the throttle body might help as well with the idle and engine response, so I did both as they are sequential parts of the air intake system.

There was not a complete DIY on Club Lexus for either process, so this post was created. My thoughts and DIY notes are as follows on cleaning the MAF sensor and throttle body (as the GS430 engine is structurally similar to the GS400, these instructions apply; LS400, LS430, SC400, SC430 V8s are also very similar):

OVERVIEW
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)

BEFORE YOU START--ALWAYS DISCONNECT THE BATTERY (and mark down your radio stations as you'll lose them). MAKE SURE YOUR CAR IS COOLED DOWN OR YOU WILL BURN YOURSELF.

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. Now onto the throttle body cleaning...