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MAF Sensor and Throttle Body Cleaning DIY: GS400 & GS430

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Old 03-28-08, 08:32 AM   #1
SeattleGS400
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Default MAF Sensor and Throttle Body Cleaning DIY: GS400 & GS430

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...
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Last edited by SeattleGS400; 03-29-08 at 10:51 AM..
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Old 03-28-08, 08:33 AM   #2
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Default MAF pic 2

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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Last edited by SeattleGS400; 03-28-08 at 10:00 PM..
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Old 03-28-08, 08:34 AM   #3
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Default Throttle Body Cleaning

2. Throttle body cleaning.
a. Remove the plastic engine cover (2 bolts, 2 screws).
b. Take off the air intake tubing system starting from the air filter box (loosen the compression end clamp), the plastic vacuum recovery box [disconnect 3 vacuum tubes (slide off the metals clamps about 1" from the edges, then slide off the vacuum hoses—power steering hose, EVAP hose, PCV hose (shown but not labeled in the schematic directly below--you do need to disconnect it, see post #9 for schematic with the label on it); remove the 2 bolts that hold the vacuum recovery box to the engine block (one is at the top of the box, towards the car’s dash; the other is towards the passenger side of the car)], and finally the other end of the tubing system that attaches to the engine’s throttle body (where you’ll need to loosen the compression end clamp). This whole assembly comes out to expose the throttle body at the front of the engine.

I used the following cleaner for the throttle body:

Valvoline SynPower Carb, Choke, and Throttle Body cleaner [$4 from Schuck's]

I sprayed a moderate amount of cleaner onto a clean cotton shop towel and cleaned the throttle plate valve. Then, I used another clean shop towel to help prop the valve open (push the valve on the top part towards the engine, as the valve swings) so I could wipe the back of the valve and more of the valve body distal to the throttle plate valve (I could reach about 2-3 inches past the throttle plate valve). I would recommend wearing vinyl/latex/nitrile gloves as this cleaning portion is rather messy with the sludge from the engine. And remember, don't clean the engine if it's hot, as you WILL burn yourself!!!

Reassemble the parts in reverse order of disasembly. Reconnect the battery. Congrats, you're done and ready to reap the benefits your work!

NOTE 1: When you swing open the throttle plate valve during cleaning, I believe that fuel gets into the cylinders, so when you get all of the intake hosing reconnected and start it up right away, your car might transiently idle roughly (much like a flooded engine). However, if you waited a few hours after this procedure, the fuel will evaporate and you won't have this issue upon restart.

NOTE 2: After you are all done and reconnect the battery, the ECU will be reset and will relearn your driving style (i.e. how fast to upshift, how aggressive you are with your throttle, etc.).
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Last edited by SeattleGS400; 03-29-08 at 12:46 PM..
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Old 03-28-08, 08:38 AM   #4
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Default Throttle Body: Closed valve

Pic of the throttle body closed. Notice how dirty the valve edge is with deposits--you'll need to clean the edges and the main throttle body. Use throttle body cleaner sprayed onto a cotton shop towel. You will need to wipe and rewipe the area to get it totally clean.
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Last edited by SeattleGS400; 03-28-08 at 09:06 AM..
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Old 03-28-08, 08:40 AM   #5
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Default Throttle Body: Open valve

Notice how dirty the throttle body is upon opening the valve. You push in the top portion of the valve, and it swings open. You will need to WIPE clean the deposits off the throttle body and valve with a cleaner soaked cotton towel(s). You will need to wipe and rewipe to get it clean enough to do the job. I wouldn't suggest spraying the cleaner directly into the throttle body as you won't be able to wipe it all off. Wear gloves when you clean the valve and throttle body or you'll get some very dirty hands.
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Last edited by SeattleGS400; 03-28-08 at 09:27 AM..
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Old 03-28-08, 08:42 AM   #6
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Default Impressions and Recommendations on the MAF Sensor and Throttle Body Cleaning

Impressions. After MAF sensor cleaning and throttle body cleaning, and driving around town, I immediately noticed my car idling a bit smoother while parked in gear. The throttle response subjectively appears more immediate (it used to have a "delay" when you push on the gas, and when the car actually realizes it has to "go"). Next, subjectively, the car seems a bit more powerful. I also noticed that my gas mileage seems to be improved by about 2 mpg in combined city driving (under two tanks after cleaning the MAF and the throttle body)--probably due to the fact that the engine no longer runs rich.

Recommendations. When you change your air filter (once every 2 years), this would be a good time to clean your MAF sensor with the appropriate MAF-specific cleaner (like CRC MAF Sensor cleaner), and clean out your throttle body and valve with the appropriate cleaner (like Valvoline Carb, Choke, and Throttle Body Cleaner). This will help your car idle better, get better fuel efficiency, and run optimally with improved throttle response and performance. Total time: about 30-45 minutes. Total cost: $10.

Last edited by SeattleGS400; 03-28-08 at 08:50 AM..
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Old 03-28-08, 09:05 AM   #7
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Default MAF and Throttle Body Cleaners Used

1. CRC Masss Air Flow Sensor Cleaner [$6 from Schuck's Auto Parts]
2. Valvoline SynPower Carb, Choke, and Throttle Body cleaner [$4 from Schuck's Auto Parts ]
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Old 03-28-08, 08:42 PM   #8
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Default

EXCELLENT POST
I usually remove the entire throttle body assembly to clean inside, but this is great. I haven't removed the mass air flow sensor to clean it, so I will definitely try it. I usually spray it thoroughly and let it dry completely before re-installing it.

The entire throttle body assembly comes apart by removing the front 4 bolts and the small coolant line on the driver's side. The 2 throttle cables also have to be removed, as well as the snap in wiring harness to the TPS on the passenger side, and the throttle motor wiring on the drivers' side.

The entire throttle body complete with TPS and Throttle motor comes off as one assembly, and once off, the intake can really be cleaned. The gasket between the throttle body and the rest of the intake manifold is re-useable.

My idle is so smooth I sometimes have to look at the tach to be sure the engine is running. I cleaned this after I changed both engine mounts and the transmission mount. No problems even after 172,000 miles. The Torquemaster spark plugs also don't hurt. They have been in forever with no signs of giving up. Definitely worth the money. I also don't use K&N air filters anymore because of K&N Filter Oil being drawn into the intake.

The stock paper filter is fine.

You are to be commended for posting this great DIY complete with pictures.
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Old 03-28-08, 10:16 PM   #9
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Default Throttle Body Schematic

GSEREP1:

GREAT suggestion. It looks like it's just a few more bolts, harnesses, cables, and coolant hoses to get the throttle body apart to allow a more complete and easier cleaning of the other side of the throttle body. Once you get the whole throttle body out, how much can you accessibly clean inside the engine? I may try this next time I take apart the intake system. Per Lexus manual, it looks like the gasket SHOULD be replaced, but it's probably reusable--I haven't taken the throttle body apart yet, but again, the gasket can't be that expensive to buy.
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Old 03-28-08, 11:51 PM   #10
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You are right,
The gasket does not cost too much. Just a few dollars..(10 to 12 bucks.)
You can really get into the intake when the throttle body is removed. I had to do this procedure when I changed my starter. Toyota knows how to make maintenance quick and easy.

The throttle body stays and the rest of the intake comes out in one piece when the starter is removed. It is all pretty easy and straightforward.

I've never changed the throttle body gasket, but I will when I do the timing belt next, which is about 8 thousand miles from now.

It is amazing how smooth the engine is when the throttle body is clean. You can clean both sides of the throttle plate thoroughly and spray and clean the inside of the intake. It is usually pretty clean in there anyway.

When I do mine, I'll be sure to take pictures and post them. I'm changing the hoses and new spring clamps this time. The hoses are all original from December 1998 but they still look good. 8 years is long enough though.

my engine is clean enough to eat lunch off of. I clean it each time I wash the car. I guess I am a fanatic of sorts.

Thanks again
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Old 03-29-08, 07:22 AM   #11
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Great information. I'll look to separate the throttle body from the intake manifold next time for a more thorough cleaning--would probably make my car a even more smoother. As of right now, based on my instructions (cleaning MAF sensor and throttle body without taking it apart from the engine), it's about 80% smoother than before. I can probably get that last 20% with a complete removal and cleaning of the throttle body, per your suggestion.
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Old 03-29-08, 09:53 AM   #12
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Thank you Seattle for this great detailed DIY input! gserep1, thanks for the added remarks. I will be doing this soon to my 05/LS430.
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Old 03-29-08, 11:50 AM   #13
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Bravo!! This is a fantastic write up! I've been meaning to do both these things but keep forgetting.
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Old 03-29-08, 11:57 AM   #14
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Can you go into a little more detail or post a pic of the two bolts you are supposed to remove vacume recovery box and which hoses you are supposed to disconnect. I removed the bolt on the left side near the power steering fluid reservoir (unfortunately it was on so tight that the socket wrench bolt poppedl off into the bottom area and I spent almost 2 hours trying to get it out) but I could not find the other bolt I needed to remove, I was wiggling the box to try and see what it was connected to and it seemed like it was connected underneath the box, also when I tried detaching the thicker hose after the plastic lip of the box in the middle right side right next to the engine it would not budge. I was trying hard but it would not come off and I was afraid of riping it or breaking something. I then just tried pulling the filter hose off the throttle body to see if I could get to it without taking the recover box off but that hose would not budge, I loosend the clamp heavily and it still would not budge or give any even after putting alot of muscle into it. It felt like it was welded on, I gave up after that before I broke something expensive and just put everything back on. I was pretty pissed because I thought it was going to be a pretty quick simple process but like usaul it ended up being needlessly complicated and nothing got accomplished aside from wasting time.
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Old 03-29-08, 12:26 PM   #15
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Quote:
Originally Posted by UDel View Post
Can you go into a little more detail or post a pic of the two bolts you are supposed to remove vacume recovery box and which hoses you are supposed to disconnect. I removed the bolt on the left side near the power steering fluid reservoir (unfortunately it was on so tight that the socket wrench bolt poppedl off into the bottom area and I spent almost 2 hours trying to get it out) but I could not find the other bolt I needed to remove, I was wiggling the box to try and see what it was connected to and it seemed like it was connected underneath the box, also when I tried detaching the thicker hose after the plastic lip of the box in the middle right side right next to the engine it would not budge. I was trying hard but it would not come off and I was afraid of riping it or breaking something. I then just tried pulling the filter hose off the throttle body to see if I could get to it without taking the recover box off but that hose would not budge, I loosend the clamp heavily and it still would not budge or give any even after putting alot of muscle into it. It felt like it was welded on, I gave up after that before I broke something expensive and just put everything back on. I was pretty pissed because I thought it was going to be a pretty quick simple process but like usaul it ended up being needlessly complicated and nothing got accomplished aside from wasting time.
CLARIFICATION AS REQUESTED FOR UDEL

1. Vacuum recovery box bolts (2 total). One bolt is facing the passenger tire side, as you've found. The other is on the side that faces the main firewall towards the dash (think of a straight line on the vacuum box, starting from the front bumper straight to the car's front console dash--the bolt is on the far end of the plastic vacuum box, closest to the firewall/interior cabin). See attached pic from another post (courtesy of e-man) that I modified for clarification.

2. Vacuum hoses and loosening (3 total). The Lexus schematics in this post should be pretty clear on which ones you need to remove. You will need to slide the metal clamps about 1" away from the edges before you can move the hoses off--you do this by first squeezing with pliers the metal clamp ends together (which makes them larger) and then you can slid them away from the ends of the hoses. To get the hoses off easier, I suggest that you first TWIST left and right the hoses, then pull them off. If you try to pull them off without loosening them by first twisting, they'll be very hard to get off (esp. the thick PCV hose which has a longer end attachment).

3. Intake hose loosening (the end that attaches to the throttle body on the engine). First, loosen the compression clamp. Again, TWIST the whole tube end, you may have to gently push the rubber end lips a little at a time to get it to twist off. It does come off--no glue is holding it in place (it's attached like the other end to the air filter box). It's probably never been removed on your car before, hence why you're having such a problem--have faith, it does come off
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2003, air, body, clean, cleaner, es300, evaporation, flow, gs400, intake, lexus, maf, mass, sensor, system, taking, throttle

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