Lexus GS (1998-2005) GS 400 & GS 430 Throttle Body Cleaning DIY

Clean the Throttle Body (TB) of a 1998-200 Lexus GS 400 or of a 2001-2005 Lexus GS 430

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

Source: ClubLexus

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.).

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.

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.

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.

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.


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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