So, after quite a few PM's on how to do this I finally broke down and took some pics. You will notice however that I did not put everything back to "factory settings", ie, I just took a few pictures and hope that they'll help the ones who want to know how to do this.
First off though, a warning:
****THE COOLANT WILL BE HOT AFTER RUNNING THE ENGINE, THEREFORE TO AVOID BURNS I STRONGLY SUGGEST THAT YOU LET THE ENGINE/COOLANT SYSTEM COOL DOWN BEFORE ATTEMPTING TO DO THIS, I AM IN NO WAY RESPONSIBLE FOR PERSONAL HARM THAT MAY BE CAUSED WHILE ATTEMPTING THIS, YOU HAVE BEEN WARNED****

STEPS:
1:) You want to start by disconnecting your SRI/CAI/Stock Intake at the throttle body:

2:) Disconnect the 4 Vac lines (three on top, one that sits lower):

3:) Disconnect the Throttle Cables (one for Man, two for Auto):

4:) Remove TB by pulling the 4 12 mm bolts:

5:) Remove TB from Intake Plenum:

6:) You will notice three lines hooked into the TB, two outside line (coolant) and one middle line (vac). You want to "bypass" the TB by linking the two coolant lines together, using a 5/16th brass bard (male to male) fitting and screw clamps to tighten it down. Please do not use existing hardware as its probably been sitting there for a while and chances are it wont stand up. Please use new hardware (screw clamps).




7: After you insert brass barb (male to male fitting) and tighten down the screw clamps, you might want to install some vac caps on the coolant ports. Although I cant say if its required, for me its just piece of mind):

8: Reattach the Vac line (its the middle port)!

8.5: Totally optional, but at this time I did a minor cleaning of the TB, and the butterfly valve. Not required, but while its open, might as well, right?
9: Check your work. This is what you should have, two coolant lines "looped" together, two coolant ports capped (optional), and the Vac line (the middle port) reattached. Make sure that your screw clamps are tight (either use a socket or the right size four point to make sure its super tight...don't want leaks), and again, check another time. Once you are sure everything is done, place your throttle body back on the intake plenum, place the SRI/CAI/Stock Intake back on, and enjoy!

While I can not say this is how it is for different engines, the concept is the same. So, for all those people PM'ing me, this is how you do it (again ,mind you its not a pure step by step, but you'll get the idea), and for those who want to know how to TB Bypass on the 5SFE, here you go!
I hope this can help answer this question to some extent. If anyone sees anything wrong with this (ie mislabeling please let me know so I can correct).
Thanks and hope you enjoy!

Very nice write up!

vote for sticky!

sticky!

Not to sound like a dick but those are there for a reason, toyota wasn't like hey lets put 2 random @$$ coolant lines into the intake. They're there for proper idling when cold. Also removing them doesn't accomplish anything, the air you intake is moving to fast to be affected.

You can remove a lot of things off a stock motor(egr, thermostat, iac lines, exe.)without major problems, BUT it will cause problems down the road.

Now Im not telling you what to do but other people need to hear both sides of the story.

Very well put together How To:, good job spider77

This post has been edited by hatchy_gt-s: Oct 24, 2010 - 10:31 PM

i just dont understand why toyota would run coolant throught the trottle body in the first place.. if it didnt have it, the heat from the engine is still heating it up.. and as for cold starts... hahah well the coolants going to be cold to. and if there worried about freezing, they shouldnt worry unless you dumped water into your intake in the middle of winter. i agree with hatchy gt-s, we should hear both sides, but how would this affect idle? and cold starts?

Well, the one reason why I had it set up like this is because it is fairly easy to hook back up the way it was. Seriously, the hardest part about this is removing the TB from the intake plenum. As far as Idle problems, I have not experienced any yet.

sorry for the newb question, but what is this for in the first place? i dont get it!

coolant runs through your throttle body making it very warm.. the down side to any engine it taking in warm air, you car wants the air it takes in to be as cold as posible, so bypassing the throttle body helps with taking away that warm water going around it.

>

i was thinking if the effects of doing this will be negated if you have an alluminum intake pipe. because as your engine gets hotter, the intake pipe will get hotter too and this could heat up the air coming in. although, i'm not sure which is hotter. but the thing is, the area that the coolant heats up is much smaller that the intake pipe specially if you have a CAI setup.

what do you think?

i have to agree with spider77 since we live in Texas and it doesn't get to cold during our winters, so there is no point to have our intakes heated up and like what he said if it does get cold enough to need it is just a matter of hooking it back up. But for our hot as hell Texas summers we don't need our intakes warmed up.

it's not meant to heat the intake as such it's to prevent the throttle freezing/sticking open when really cold afiak

>


Stumbled upon a relevant patent, priority date July 12, 2000, that showed three coolant 'bypass' passages, relatively independent water channels that lead from the back of an engine to the front (water pump), inside of (bypassing) the coolant pathways to and from the radiator. It showed no thermostat, as it uses a computer controlled FLOW CONTROL VALVE to switch from full flow through the TB when the engine is cold, to no flow through the TB when the engine is hot (the situation that spider77 creates. . . permanently).

One of the passages was just a pipe from the back to the front (called RESTRICTION in the patent).

One passage went from the back of the engine through the heater and then back to the pipe leading to the front.

The third passage went through the Exhaust Gas Recirculation (EGR) valve , then through the throttle body (TB), then to the FLOW CONTROL VALVE, and then back to the pipe leading to the front.

You can imagine them as three parallel 'bypass' coolant passages, at least at the point where hot water comes out of the operating engine. They don't all carry coolant all the time (e.g., the heater only carries coolant when you turn your heater on). But they can (e.g., the passage through the EGR valve and TB), unless the computer instructs it to slow or close.

A fourth passage in the patent was the main one, the passage that goes out to your radiator and then back into the engine.

The patent showed the EGR/TB passage and the Radiator passage coming together at a FLOW CONTROL VALVE, so the computer would have the ability to control how much coolant moved through the TB. Evidently, this newer design would allow the computer to completely cut off the flow through the TB once the engine reaches its normal operating temperature.

The main claim of this patent was that by control of the flow through the TB they were able to cut the warm-up time of the engine from something like 250 seconds to something like 187 seconds.

Not being privy to the design decisions that Toyota used to set up any of its engines, I took this to be the reason that they piped coolant through the throttle body. It's a way to significantly decrease the time it takes to get the engine from ambient temp up to normal operating temperature. Every time you start your engine, you have to go through this 'warm up' period, even if you live in the hottest part of Texas. The operating temp of an internal combustion engine certainly must be much hotter than that.

I believe the overall engine design depends on operating temperature to a great extent, so getting to that point quicker, in an ordinary car, has benefits that none of us has the background to truly appreciate.

Now, on our older vehicles, on the other side of the issue we have 'shorted out' one water cooled/heated element (TB), intending on preventing a hot TB from heating up the intake air, which only matters when the engine has reached its normal operating temperature, which we have time delayed. Someone above suggested that the airflow through the throttle body was so rapid that a hot TB would not make much of a contribution toward heating the intake air. I'm not sure that's the total answer, but can offer a bit more information.

The Exhaust Gas Recirculation (EGR) system is part of your engine's emissions control. It's main function is to reduce or eliminate the generation of NOX (exhaust gasses containing oxides of nitrogen), since NOX causes smog and acid rain. NOX is created when the fuel burn occurs in a cylinder that is above a certain temperature, a temperature that would normally be reached under normal conditions, so, under certain engine operating conditions (load, temp, etc) the computer intentionally reduces the combustion temperature by adding a small amount of exhaust gas (NOTE: inert gas) which has the overall effect of lowering combustion temperature (which lowers your useful hp, and mileage, of course ).

There is a pipe that routes exhaust gas directly from the exhaust manifold back to the EGR valve, which controls the amount that is added back to the intake air. I'm guessing that HOT exhaust air moving into the intake air flow must have a much larger effect than what heat could be transferred by the hot coolant continuously running through the TB. But, then again, the EGR doesn't turn on all the time. It's off at idle. It comes on only when the engine temp reaches a certain value, and even then when there is significant load on the engine. So, it's hard to know for certain what is best for your engine.

The only reason I know this stuff is because I just finished troubleshooting and fixing a CHECK ENGINE LIGHT (MIL) that came on due to a 'excess EGR flow' code P0204 (?) on my 2000 Tacoma. Found a bad Vacuum Switching Valve (VSV). While at it, I took apart everything up to the intake plenum to clean out all the carbon, varnish and whatnot out of my TB. When I went to put it all back together I ran across those stupid water hoses and had a devil of a time figuring out how to connect it all back up properly. That made me search and read a whole lot about the subject at hand, and during that exercise I ran into videos on YouTube that showed exactly what Spider77 shows you how to do at the top of this thread (and Spider77 did it so well he should be much appreciated).

Yet, I wondered deeply why someone would do that, and concluded that it would definitely be a help if one had a race car engine that doesn't have emissions controls on it. Because then every minute contribution of heat going into the engine air intake would need to be eliminated. Other than that, I really don't see the true benefit (it's got to be a trade-off), and I worry that there is a detriment to the long term operation of your engine due to extended lengths of warm up times.

Main question is there any gain in doing this?

Nothing that can be measured reliably.

>


And the flip side. . . is there any loss?

Bitter probably has the right answer to both questions. My opinion: it is worse to shunt (bypass) the TB because it would shorten the life of the engine (by some unmeasurable amount, Bitter would correctly add).

It's there to prevent icing of the throttle plate and IAC under certain driving conditions, like high humidity and medium to lower ambient temps. The pressure drop across a small opening like the throttle plate can cause the air to be cold enough to condense the water out and freeze it. Ice in your throttle is bad, in the IAC it stops it from being able to idle the car right or at all. Typically the heat conducted through the metal intake manifold would be enough, but if you've just started driving and the intake manifold is cold there's a potential for icing. The hottest coolant available is routed for the throttle, so it warms up fast and prevents icing. The amount of surface area in the throttle body, the speed at which air passes through, and the time which it has to absorb heat through contact (not to mention the insulating effects of the boundary layer) mean that very very very little heat is gained there. You'll pick up more heat from the intake manifold and cylinder head port than the throttle body I would think. It's one of those 'I did this thing and spent time on it and it cost me nothing so yes it definitely did something', though I really doubt it does.

Do it, don't do it, odds are there's no gain and very little chance you'll ice the throttle body. Just remember though, auto makers are the ultimate penny pinchers and they always heat the throttle body, they must have some reason.

I examined the Idle Speed Control Valve when I had my throttle-body off and was trying to get it to idle right.
On the back side of the ISCV is the cover plate with two small screws, and it is slightly adjustable. I meant to take some pics of this while I had it off but ran out of time.
inside there is a slot-n-groove contraption that holds a Bi-metal spring in place. now, the idle speed is controlled by turning the little valve inside to adjust the exact amount of air allowed into the intake when the throttle plate is closed(idling).
on the front side is the magnetic coil which the computer uses to control the position of the idle valve, on the back side of the rod that controls the idle valve is this Bi-metal spring.
a bi-metal spring is simply a device made of two different metals, maybe steel and brass or something, and as they get hot the two metals expand at different rates and cause the coiled spring to expand in a particular way that moves the idle air valve.

so it seems to supplement the control of the idle valve in some way, although im not yet sure how. The coolant lines run though passages that effect the temperature of this bi-metal spring. I am guessing that as the engine coolant warms up the bi-metal spring
expands and this mechanically moves the idle valve in the direction that closes is slightly more than it was, lowering the idle speed as it warms up.
the question is, why doesn't the computer just use the temp readings from the Coolant Temperature Sensor and adjust the idle speed accordingly??

however I'm not really sure that this is all there is to the way this system works. It's just what I guess.
maybe the general idle speed is controlled by the computer and this bi-metal spring just drops the idle a bit as the engine warms up.
This would mean a couple of things: 1. adjusting the exact position of that little plate will effect your idle speed. 2. doing the mod of this OP will cause your engine to idle too high.

>

these two pics show the back side of the ISCV and cover plate I'm talking about. under this is the bi-metal spring.
see it is adjustable.

I am most certain that the coolant runs though there Just to effect that bi-metal spring (it's more of a coil shape like inside of a cheap house thermostat)



This post has been edited by VavAlephVav: Sep 9, 2014 - 10:12 PM

It may just be a coil spring to make sure the IAC fails fully open when it fails? Maybe it is a bi-metal spring and it's a backup in case it fails electrically? Someone should take one apart and find out, I'd be interested to know.

it is definitely set up in a slot-n-groove sort of contraption so that the valve will only work one way. If you take it off and flip the valve over the wrong way when you put the spring back on the valve will not be in the right place to control the airflow at all, it will be wide open and your **** will try to idle at 4500.
I had to suck on the vacuum port while I put my thumb over the little square hole the ISCV breathes through at the bottom of the butterfly to be sure I had the valve on the right side before I put the spring back on.
so it does prevent it from being All the way open. I imagine that if the magnetic coil completely failed that little valve would just spin around on there of its own free will which would really suck.

>


That ISCV looks very similar to the Idle Air Control (IAC) valve on my 2000 Tacoma that I was discussing above. The IAC valve is attached to the TB using four phillips screws (that are hard to get loose). In that photo, you can see at least two of the four screws and see how the ISCV is connected to the TB, just like the IAC is in the Tacoma. The central feature in this photo, where you see two phillips screws, is a cover that would cover the bi-metal spring being discussed. If I remember correctly, there was some kind of cover (less striking) on the Tacoma IAC.

I didn't take that apart since it seemed to be factory preset (notice the yellow paint in the photo?). Also notice in the photo that if you loosened the two screws you could 'adjust' the preload on the spring by slightly twisting the plate and re-tightening the screws. There may or may not be such a spring in the Tacoma IAC, since it is definitely computer controlled (i.e. there is a connector coming off the wiring harness that plugs into wires in the IAC).

I looked up the TB in my shop manual for my 7A-FE engine of my 94 Celica ST, and there was an Idle Up valve that seems to be controlled by engine vacuum, but no coolant hoses running to it. She isn't home today, so I can't visually verify that.

I DID take the IAC valve off of the Tacoma TB, and cleaned and tested it according to its shop manual. Seems the function of the IAC is to allow air to bypass the butterfly valve inside the TB when it is closed (IDLE), so the IAC allows some air to be going into the intake manifold during idle, else the engine could not start.

TESTING THE IAC: When I had the IAC off, and cleaned, I could clearly see the 'valve' was a 'shutter' (rectangular metal door that sounds just like the square hole reported by VavAlephVav) that closes -- or opens to let air bypass the butterfly valve). There is, on the Tacoma, an electrical connector to permit the ECU to control the opening of the IAC valve. There are three electrical pins going into the valve, the center of which carries 12 volts (when under test) and the other two go to coil windings that control opening and closing of the 'shutter'. Two kinds of tests are done on this valve. The first test is to determine the resistance of each coil winding. Though different, these resistances are both in the neighborhood of 20 ohms. The second test is comprised of putting 12 volts on the center pin and then ground on the other two pins, one at a time, and checking to see the 'shutter' opens with 12 volts across one winding, and that it closes with 12 volts across the other winding. The solenoid may be working against. the force of a spring to insure that a failure would leaves the 'shutter' open (to guarantee an ability to idle), but I cannot say for certain. I do not know if the spring in the IAC of the Tacoma, if there is one, is bi-metallic or not.

Perhaps the Celica ISCV is identical in function to the Tacoma IAC valve, but instead of a computer voltage controlling its opening, it uses temperature to control its actions mechanically, by causing a bi-metal spring to wind and unwind, whereas the IAC on the 2000 Tacoma the ECU uses Engine Coolant Temperature (ECT) to decide how much to open or close the IAC valve? But VavAlephVav mentioned that his valve had a vacuum port that he had to suck to determine which direction to install the bi-metal spring. There is no vacuum port on the Tacoma IAC.

This post has been edited by Langing: Sep 12, 2014 - 12:42 PM

yeah, the center tube on the bottom of the throttle body is a vacuum line running to the AC idle-up valve.

guys the reason there is coolant going through the TB is to prevent it from freezing open. in certain climates where its really cold and humid its possible for it to freeze open. thats bad. so the warm water prevents that.

It has nothing to do with the IAC. that is all ECU controlled.

Smaay is correct, but what is the purpose of the spring? The meaning of life? Why does everyone like Will Smith so much? Life's mysteries man...

The spring is actually a bimetal spring and the temperature makes it relax so that the valve will close further than it would with no water running through it.

In other words, removing the coolant lines to the TB may result in higher RPM idle, until the TB heatsoaks enough for the heat on it to transfer onto the spring and relax it.

Yes the IACV is ECU-controlled but there is also a mechanical aspect to it.

Which is why next time I'm working on the engine I'm going to remove the OEM unit and replace it with a simpler stepper-type valve from a VW or a GM engine. (standalone ECU perks)

Ford IAC's are easy to work with also, but they're kind of bulky, but they're nice and sell contained as well with just a flange needed.

>

With that strong throttle spring that immediately closes the butterfly valve whenever you take your foot off the pedal, there are really places cold enough with high humidity conditions that can freeze the throttle wide open? For real? Are you absolutely certain? Like people drive their cars on the Bering Sea, maybe? Any place where the temperature drops well below freezing, I would think the humidity drops correspondingly as moisture in the air freezes. That should be true unless you are tossing sea water through your air filter, TB, and into your intake. Yet here is a fellow from Chicago (pretty cold there) who claims that a fellow from Southern California (pretty not cold there) is correct in stating this as fact. Can anyone cite a reference to validate their claim?

Hey, I sorry if I seem stupidly stubborn, but I learn something new every single day, and I am happy being wrong when I am because I learn from mistakes. I've actually never heard of a throttle freezing (like from ice) wide open, and can't imagine a way for it to happen in a real car driving on earth. Maybe when it is "really cold" (like way below zero F) the intake air, being so damn cold, doesn't require much moisture in the TB for it to freeze, or maybe it is just at the point of freezing where it becomes a problem? Maybe it has something to do with the physics of the formation of ice crystals or something? If true however, someone please show me a reference so I can believe it. If not a reference, has anybody experienced this phenomenon personally?

I remember people on this website who swore to me that cast iron absolutely could not bend without shattering, yet, after spinning my wheels over that true belief for almost a month, I was finally able to demonstrate that proposition wrong when it comes to the steel that is used to make Toyota steering knuckles, plus I found six incidents posted on Toyota car websites where other people reported bent ears on steering knuckles. Some fellow on this website even reported Pep Boys heating the ears on his steering knuckle and bending them back in place (how they got them perfectly straight I'd still like to know). Without a shred of doubt, the ears on my steering knuckle were bent. Another one put in its place solved my rotor dragging problem.

In conclusion, when I examined the illustrations in my 1994 Celica ST shop manual this afternoon, I could not find coolant hoses going to and coming from the TB. So, what you guys are telling me is that, given the right weather conditions, my Celica's throttle can potentially freeze wide open?

Pressure drop causes the air to condense and cool to a greater degree than ambient conditions. That's why airplanes have carb heat elements to prevent icing. Given the right weather conditions the throttle could form ice which could cause it to stick or the IAC to stick. It's not going to create ice at WOT because there is less pressure differential. If it's going to ice, it would be at steady state low throttle cruise when manifold vacuum is the highest for the longest amounts of time, or when engine braking down a steep grade for a long period of time. It's more of a problem with carbs since the fuel charge is evaporating and removing more heat from the air. Pressure temperature relationships are cool. Get it?

>

Agree that pressure/ temperature relationships are cool. Sometimes they lead to counterintuitive realities. Thanks for stepping up to the question. What you said is making sense.

You did a slight gloss-over when you said "Given the right weather conditions the throttle could form ice." Can the throttle form ice without the presence of moisture, such as when the ambient air is extremely cold? In the deep of winter, even here in NC, the ambient air is quite dry, as any moisture has precipitated out. Homeowners frequently run humidifiers in their homes to keep some moisture in their inside air, to make themselves more comfortable, or to eliminate static electricity.

If I understand you, ice formation in the manner you describe (pressure drop), the weather conditions would be in the neighborhood of 'near freezing' rather than deep freeze conditions. For ice to form in the TB, there must be moisture (water) in the intake air. In a deep freeze situation there is no moisture, so no ice can form. Or is my understanding incorrect on this point?