Article: Cleaning the Throttle Body

[ninz30]

i will be doing this soon! Awesome write up

[pinkgrips236]

Just a quick question for those of you that have removed/installed TBs :

how necessary is it to drain the coolant before pulling the TB? the manual says to drain it, but I just put all that darn stuff back in there!

will I get a few bits of spillage, or am I looking at losing it all anyway if I don't drain it.

[timsrv]

Fortunately the throttle body is the high point in the system. I would pull the radiator/filler cap & drain about a cup out of your radiator petcock. After that you should be able to pull the TB hoses & work on it with little more than a few drips. Tim

[ninz30]

I thought you only had to drain the coolant if you remove the upper intake manifold?

the two hoses on the throttle body are by-pass hoses and will hardly leak at all.... Tim is right tho just drain a cup or so

[pinkgrips236]

I wound up draining about a cup of coolant. When the TB finally came off, no extra coolant spilled out.

The two bypass hoses are pretty worn looking, so we'll go for some new ones.

With everything off, I'm thinking about replacing the vacuum hoses for the TB. They all read #0 which I'm guessing is the size of the hose?

[timsrv]

Here's a quote from another thread:

Regarding the vacuum line (the small stuff like what runs across the top of the throttle body), this can be substituted for standard aftermarket sizes at the parts store but I've found the fit isn't perfect (either too small or too big). The small is more secure and less likely to fall off, but pushing it over the nipples stretches it a bit beyond it's design limitations (makes it prone to cracked ends). The other problem is the little looms that fit over the hose (for organization) don't fit the aftermarket stuff right. For this reason I prefer Toyota vacuum hose. Toyota sells it in predetermined lengths from 300 mm (about 1 foot) to 2600 mm (about 8 1/2 foot). Here's the Toyota part numbers & current pricing (at the time of this post):

• 90999-92002 300mm $5.46 (~$5.46 per ft)
• 90999-92003 600mm $2.53 (~$1.26 per ft)
• 90999-92004 950mm $13.33 (~$4.44 per ft)
• 90999-92006 1300mm $21.38 (~$5.35 per ft)
• 90999-92007 1650mm $36.78 (~$7.36 per ft)
• 90999-92008 2600mm $52.18 (~$6.14 per ft)

Note, this is current MSRP (what you'd pay if you walk into your local Toyota parts counter). If you order it via one of the discount Toyota parts sites, you can save up to 30% (before shipping), but as you can see, the cheapest way to get is purchasing in 600 mm lengths (about 2 ft). The good news about this size vacuum hose is Toyota uses it on almost everything they make so they're not likely to run out any time soon. Tim

[bareskier]

my latest and most current need for help is with the throttle body rebuild. everything is off and ready to go into the chemical bath but... the screw under the rubber cover (idle screw) backs all the way out but stops short by 1/4" of coming out of the hole. i've tried air- but with no joy. the screw just spins after backing it out. it will tighten back down each time but after several tries to unscrew it, it just wont go that last bit so i can get a grip on it. what am i missing in the process?
i'm stumped. anyone have any suggestions?
thanks- mike

[timsrv]

I assume you've already read the 1st post in this thread.........right? That screw has an o-ring on the head, and it grips the bore (makes it hard to remove). I use a screw holding screwdriver & it comes right out every time, but if you don't have one it might be a PITA. Air should work, but it can be difficult to seal your air gun against the port. A rubber tipped air nozzle would work much better than a standard one. Tim

[bareskier]

thanks tim for the soft knock on the head. i do remember reading the post with the link and thinking - wow , i finally get to use my starter screw driver after all these years its sat in my tool box neglected.
it must be that forest and the trees thing. or more likely the aging process at work.
i got it out in seconds. thanks
where can i pick up a gasket for the t body, toyota wants too much and will take too long. do any other vehicles use this same t body gasket - do you or anyone know? also what is the name of the lube with pfte you use for the seals and o-ring.
my idle screw was 1 3/4 turns to bottom. sound about right. how would one remedy this once installed without pulling it apart again? would this keep it from starting or just idle crappy??
thanks as always for the assistance. - mike

[timsrv]

If you don't want the Toyota gasket, then start calling auto parts businesses. I'm guessing it's a dealer item, but somebody might have one. If you find one on the cheap, please post so the rest of us will know too. There's always the paper stuff they sell for cutting out your own gaskets too. That lube I'm using is Radio Shack part #64-2301A. I use it because I like the applicator, but I'm sure others will work just as well. I've had it for years, so wouldn't surprise me if they don't carry it anymore.

That screw is simply to make fine adjustments to your idle speed. 1 3/4 turn is just the starting point or approx setting. If it's off, the worst that can happen is your idle RPM's might not be exact. It won't affect starting. Once it's been warmed up and the timing has been set, you use that screw to set the idle speed. Tim

[bareskier]

greetings
i assembled the t body and hit a stumbling point. or maybe everything is as it should be. my t body was encrusted with carbon and black soot at the start so i could not tell to note whether or not my finished job is correct or not.
it appears to work as intended but the shaft and disc come to rest at an angle a little less than 45 degrees. it does not close flush.
looking down thru the top of the throat, with the body oriented with the water hose side facing me the disc is angled downward towards me and the screw slots are facing me.so i know the shaft is installed correctly. the shaft and disc come to rest disc high in the rear angled downward toward me. at this point there are little air gaps at top and bottom and appear to be even in size.
should these gaps at the rest point be there at all or is this normal, and is this angle of the disc at rest normal.
when i started the assembly after cleaning i placed the brass disc into the bottom of the throttle body flat by itself to see if it fit and to check the tolerances around the circumference. it fit perfectly into the opening only one way and matched my marks exactly
i pushed the disc flat into the body and it stopped passage at about 1/4 inch into the throat. i installed the shaft and placed the disc into the body throat, i had to tap it lightly down with the butt end of a wooden hammer to get past this sticky point and into the slot of the shaft ok. with it loose in the shaft slot i installed the screws loose and floated the disc while moving the shaft to find the sweet spot. i then snugged the screws up. the shaft will not close any further than described above.i repeated this procedure several times with the same results.
i finally gave up and finished the assembly and this is currently how it now sits on my bench.
i hope i have written a description clear enough for others to interperit ok. i know this could become a wordy dialogue so if you want my number instead of writing send me a pm and ill get it to you asap.id sure like to move on with this task done and behind me in working order.

anybody have any advice on this? is it right as it sits or does something else needed to be done. did i miss a step?
thanks - mike

p.s. FYI on the removal of the stuck/stubborn idle screw- i could hear the dry o ring squeaking so i screwed it back down added some drops of mystery oil, turned the screw in and out a few times and it smoothed the screw right out of the hole.

[timsrv]

The butterfly plate in the throttle body is precision machined to make an air tight seal. Even the edges are machined at an angle to match the inside bore. To start with, the shaft & the butterfly plate need to be oriented the exact same way they were before you disassembled (each side facing same direction and top and bottom same as before). This is why I suggest scratching an identifying mark on the plate before disassembling (allows for easy and correct alignment while assembling). When the butterfly and shaft are oriented as before, prior to tightening the screws, you close it tightly so it fits intimately with the throttle body bore. With the throttle held tightly closed, you tighten the screws to lock in place. If the butterfly will not close tightly against the bore or if you did not seat it as described, you'll need to go back and do it again. If you made no marks on the butterfly before disassembling, you'll need to fit it each possible combination until you find the one that allows it to close all the way and make an air tight seal. Good luck. Tim

Note: Always set the butterfly to the shaft BEFORE putting the cable guide or any other parts on the shaft. Other parts (like the idle stop screw or TPS) will interfere with correctly setting the butterfly.

[robgagnon]

I would like to contribute the following solution you might need, related to this cleaning job.

I cleaned my TB and then the engine would not idle down. It turns about that the butterfly would not totally close does due to wear in the shaft bushings (or somewhere else perhaps) and it would bind a little. And I found that it would close if there were some pressure on the shaft, the pressure being placed at the tip of the shaft so as to push it back toward the TPS. So I fabricated a 1/2 wide steel bar with a large hole and a small hole about 2.75 inches long. The large hole allows it to slide over the threaded end of the shaft, and then putting the original nut back on, it sticks straight up at idle but does not touch the engine lid. The small hole has a tension spring running back to another similar bar I have sticking up from the upper rear TB bolt. So the spring is parallel to the shaft, pulling the shaft toward the TPS. There is not really all that much tension on the spring, and it does not significantly effect the effort required to increase throttle. I can feel no difference at all actually. The fix works beautifully though it is rather hack like. It cost about $2 for the springs and bar stock might be less than $10 from a hardware store.

[beoutside]

Hey Tim
I'll probably never have a use for the throttle body that came on my used motor from Japan, I'd happily send it to you for the help I have gotten from this site.
Donny
93 previa
PS
I was getting an extra 4 miles to the gallon with this motor...... 25 mpg highway avg 65 on flat ..... left the injectors in it that it came with from japan, as well as intake manifold. I believe......
PS
can you send me the link to reading engine codes on the baby
thanks probably o2 issue.

[beoutside]

found the codes from an old post thanks though
just let me know on the throttle body
donny

[timsrv]

Thanks Donny, that would be cool. I'll PM you my address. Tim

[ratatouille]

Found a website selling the TPS at 11.99 a pop. But not sure of website...I'm kinda paranoid giving out my info these days...

http://www.brohacks.com/72discount20...r-p-12508.html

[timsrv]

Yeah, I put 5 of them in my cart and went to check-out. Before entering any personal information I checked and found it was not a secure page. If they would accept PayPal I would have completed the purchase, but there's no way I'm giving out my info on an insecure web page. If anybody else wants to take a chance, get me 5. If they actually show-up I'd be happy to pay you $20 each + shipping. Tim

Oh, and the website address "brohacks" doesn't instill a lot of confidence

[ratatouille]

Yeah I put in a fake name to get to checkout. It ran my order and said I owed payment in iTunes gift cards. Someone might be bummed when "Mr.Frankenstien" at "12345 Sesame St." doesn't pay up...

[filterway]

Tim,

i have the throttle body in my hands and i'm watching your video how to adujst TPS. On my 1988 repair manual, the values for continuity and discontinuity are 0.0224 and 0.0335. Why are you using different gauge thickness for checking continuity (0.028)?

Also, inside the intake is full of black stuff. what do you suggest to remove it?

thanks a lot

Jerome