1fz-fe EGR disable ?

7schulz

 
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I have searched and all I could come up with is how to do this on the 3fe. I don't want to do the block off plate, is there a way to switch some vacuum lines. I don't have to smog check any vehicles here. A picture would be great, similar to the color coded picture I found for the 3fe.
 
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Block the vacuum lines from the intake. To disable the EGR temp sensor you can simply jump the connector for the temp sensor.
 
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Ebag- has it been confirmed that we need to block the lines from the intake in order to disable the EGR? I hadn't read any conclusive evidence one way or the other, so please fill me in- I've been gone for a bit.
 
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Ebag- has it been confirmed that we need to block the lines from the intake in order to disable the EGR? I hadn't read any conclusive evidence one way or the other, so please fill me in- I've been gone for a bit.
Blocking the lines from the intake prevents the modulator from opening. If the modulator opens, then the EGR system is active.

The modulator can also fail open, which means even if you block the vac lines there will be exhaust gas dumping into your intake.
 

7schulz

 
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Any picture of the corret line to block? Do I have to block the temp sensor? If I don't will it throw a code?
 

Pin_Head

 
 
 
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I'm not convinced that disabling the EGR is a good idea. On EFI engines, the EGR is critical to cool the combustion temperature so that the ECU can run a lean burning mixture and advanced timing for better fuel economy during high speed cruising conditions. It isn't just about smog like 1970s EGRs. If the EGR isn't working, the combustion temp may be 300-400 F higher and the engine is more likely to have problems with preignition. I have seen some pictures of melted 1FZ pistons posted here and it makes me wonder how it happened.
 
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Any picture of the corret line to block? Do I have to block the temp sensor? If I don't will it throw a code?
Try this thread. I recommend you read the whole thread as there's lots of good feedback and comments past post #1.
https://forum.ih8mud.com/80-series-tech/308200-disable-egr-system-mostly-toyota-way.html

I'm not convinced that disabling the EGR is a good idea. On EFI engines, the EGR is critical to cool the combustion temperature so that the ECU can run a lean burning mixture and advanced timing for better fuel economy during high speed cruising conditions. It isn't just about smog like 1970s EGRs. If the EGR isn't working, the combustion temp may be 300-400 F higher and the engine is more likely to have problems with preignition. I have seen some pictures of melted 1FZ pistons posted here and it makes me wonder how it happened.
I've gone into this several times so I won't rehash it all, but to sum up....

1) The 1FZ was designed to run without the EGR system. And it does so on non-US spec vehicles. (Think about where the EGR pipe runs and tell me that's a great design.)

2) Tons of people have run with failed EGR modulators, either failed closed (meaning the exhaust is not getting dumped into the engine) or open (meaning it's getting dumped in all the time). Those same people have replaced their failed EGR modulator and seen zero effect on gas mileage. A few people have posted up maybe +1-2 MPG, but plenty of people have posted up -1-2 MPG. And realistically 1-2 MPG is too close to accurately decide whether the EGR system effected it or not, it's easily attributable to other factors. Personally I have seen zero effect in my MPG when I took my working EGR system and disabled it.

3) The EGR system will not have a 300-400 degree effect on the system.

4) Even if the EGR system did have that much of an effect, it would nearly exclusively be on cylinder 6, which is the most common HG failure point.

5) The EGR system dumps a lot of crap back into your engine. By not recycling that, you're likely keep the engine cleaner and running more efficiently.

6) Ignoring everything above, a disabled EGR system means not frying the main engine wiring. Which based on the threads/posts of people who have dealt with that is something I REALLY want to avoid.
 

Pin_Head

 
 
 
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1) The 1FZ was designed to run without the EGR system. And it does so on non-US spec vehicles. (Think about where the EGR pipe runs and tell me that's a great design.)
Sure, but on these engines, the ECU probably doesn't lean out the mixture and advance the timing during high speed cruise.

2) Tons of people have run with failed EGR modulators, either failed closed (meaning the exhaust is not getting dumped into the engine) or open (meaning it's getting dumped in all the time). Personally I have seen zero effect in my MPG when I took my working EGR system and disabled it.
If the ECU detects a problem with the EGR, it sets the MIL and my guess is that it does not run lean and advance the timing. Many people here are trying to fool the ECU into thinking the EGR is working when it isn't, so this may not be a good idea. If there is no benefit in MPG (I didn't see one either) then why bother?

3) The EGR system will not have a 300-400 degree effect on the system.
It is well documented that it decreases the combustion temperature by 300-400 degrees. This is why it reduces NOx.

4) Even if the EGR system did have that much of an effect, it would nearly exclusively be on cylinder 6, which is the most common HG failure point.
It is indeed our misfortune that HGs tend to fail, but why would higher combustion temperatures make this situation better?

5) The EGR system dumps a lot of crap back into your engine. By not recycling that, you're likely keep the engine cleaner and running more efficiently.

6) Ignoring everything above, a disabled EGR system means not frying the main engine wiring. Which based on the threads/posts of people who have dealt with that is something I REALLY want to avoid.
No doubt there are some down sides, but compared to destroying a piston from high temps or preignition, this seems like small potatoes.
 
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Blocking the lines from the intake prevents the modulator from opening. If the modulator opens, then the EGR system is active.

The modulator can also fail open, which means even if you block the vac lines there will be exhaust gas dumping into your intake.
Ebag- in the other (big) EGR thread, you stated that you weren't sure whether the EGR temp sensor mod alone will actually disable the EGR modulator, or whether one would need to block the vacuum lines, as well. In fact, you said you needed to test it out to see. What you state here makes it sound conclusive that blocked vacuum lines are needed. What happened in between? Have you done the test you talked about?
 

7schulz

 
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I respect this guy alot, and is a valve-train engineer for CAT. I worked with him for a couple years, This is what he said in regards to EGR's

Yes egr will lower in-cylinder combustion temperatures and control NOx better by doing that. It also gives slightly higher gas mileage. The EGR gas itself is very hot (but much cooler than the in-cylinder combustion temps would be, so it cools in-cylinder). But being hot going in, it might cause some thermal expansion for that cylinder different than others, which just might have some gasket affect. Don't know on that. If the engine was designed with it, it is calibrated for it. If you wanted to take it off, you would need a different computer chip calibrated to not have it, basically the setup they have in other countries where it is not used. This is likely much more trouble than it is worth. Generally, I like to leave highly engineered products stock!
 

96r50

 
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3) The EGR system will not have a 300-400 degree effect on the system.
I was under the impression that a drop in combustion chamber temperatures and the subsequent reduction in NOx levels is one of the main reasons for the EGR.

4) Even if the EGR system did have that much of an effect, it would nearly exclusively be on cylinder 6, which is the most common HG failure point.
The only thing exclusive to cylinder 6 with regards to the EGR is that the exhaust that is re-injected is scavenged from the exhaust manifold of cylinder 6. This scavenged gas is dumped back into the intake manifold an flows into every cylinder.

5) The EGR system dumps a lot of crap back into your engine. By not recycling that, you're likely keep the engine cleaner and running more efficiently.
I think the PCV system is a bigger culprit here. Put on a catch can and minimize the oil in the intake and the exhaust soot will flow right through.

6) Ignoring everything above, a disabled EGR system means not frying the main engine wiring. Which based on the threads/posts of people who have dealt with that is something I REALLY want to avoid.
Agreed, that does not look like a fun problem to deal with. $10 in heat wrap solves it though.

:cheers:
 
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Sure, but on these engines, the ECU probably doesn't lean out the mixture and advance the timing during high speed cruise.
Actually it does. The ECU is designed specifically to run on gas anywhere from crap (retards the timing) to high quality (advances the timing). I think it was Brian4x4 who referenced an article where they talked about how the engine was designed to run in a wide range of scenarios, and would adjust the timing appropriately.

Which brings us to....


If the ECU detects a problem with the EGR, it sets the MIL and my guess is that it does not run lean and advance the timing. Many people here are trying to fool the ECU into thinking the EGR is working when it isn't, so this may not be a good idea. If there is no benefit in MPG (I didn't see one either) then why bother?
Untrue. The ECU will set the MIL, but it does not effect the way the engine runs. I ran for almost 1k miles with the EGR system disabled and no engine codes, same gas mileage as thousands of miles with the EGR system in perfect working order. Since the weather changed and it got cold enough that the EGR CEL is coming on....guess what? Same gas mileage.

The point of fooling the ECU is to avoid the CEL. That's the only thing it does.

And in fact Mr. T provided a way of disabling the EGR system in the OBD-I trucks. There's an actual Toyota part that you can purchase (if you can find one, last I checked they were out in the US) that will bypass the EGR temp sensor and will preven the CEL from being thrown.


It is well documented that it decreases the combustion temperature by 300-400 degrees. This is why it reduces NOx.
In some vehicles. Not necessarily in the 1FZ.

Plenty of people drive around with plugged or disabled EGR systems (and the EGR temp sensor not bypassed) and no CEL is thrown. Why is no CEL thrown? Because the ECU believes that the engine is in the correct operating temperature without the EGR system active.


It is indeed our misfortune that HGs tend to fail, but why would higher combustion temperatures make this situation better?
Corrolation != Causation, so I cannot say for 100% sure that the EGR system causes it, but it's certainly likely. It could be a couple of reasons.

One possibility is the varience in temps. If cylinder 6 is running significantly cooler than cylinders 1-5, then the temp difference could cause stress that could cause it.

Someone else (Bear80) did some research and found that an engine that runs too cool can cause something called head gasket creep.


No doubt there are some down sides, but compared to destroying a piston from high temps or preignition, this seems like small potatoes.
Where do you get the idea that you will be running so hot that you will destroy a piston by disabling the EGR system?

The EGR system is disabled under heavy loads, accelleration, WOT, etc. In other words when the EGR system is disabled is when the engine will run it's hottest and be under the most strain and stress.

The EGR system is only active when you are cruising, which is when the engine is under very little stress and going to be running cool. During high speed cruising you have tons of cooling (maximum air flow) and very little load so there's no heat build up. The engine doesn't need to run cooler under those circumstances as it's already naturally running cooler than it would in comparison to driving around town, for instance.

And I have not seen a single case in the thousands and thousands of posts I've read that's indicated that the EGR system caused a piston to fail or an engine to ping. If that was the case, shouldn't we hear widespread failures from the thousands and thousands of people overseas running 80's without an EGR system?


Ebag- in the other (big) EGR thread, you stated that you weren't sure whether the EGR temp sensor mod alone will actually disable the EGR modulator, or whether one would need to block the vacuum lines, as well. In fact, you said you needed to test it out to see. What you state here makes it sound conclusive that blocked vacuum lines are needed. What happened in between? Have you done the test you talked about?
I haven't had a chance to test it yet. Blocking the vac lines works 100% for sure. I was not sure on simply disabling the temp sensor.


Yes egr will lower in-cylinder combustion temperatures and control NOx better by doing that. It also gives slightly higher gas mileage. The EGR gas itself is very hot (but much cooler than the in-cylinder combustion temps would be, so it cools in-cylinder). But being hot going in, it might cause some thermal expansion for that cylinder different than others, which just might have some gasket affect. Don't know on that. If the engine was designed with it, it is calibrated for it. If you wanted to take it off, you would need a different computer chip calibrated to not have it, basically the setup they have in other countries where it is not used. This is likely much more trouble than it is worth. Generally, I like to leave highly engineered products stock!
That is true for many vehicles with EGR systems. It is not true for the 1FZ. As I've stated, the 1FZ was designed to run and operate without the EGR system. It does not necessarily lower temps any. You do not need a different ECU/chip to operate without it. For the ODB-I trucks Toyota provided a part that will disable the EGR temp sensor without needing to swap ECU's. I have one that's in my truck that I will be removing as this doesn't work for the OBD-II trucks.

I was under the impression that a drop in combustion chamber temperatures and the subsequent reduction in NOx levels is one of the main reasons for the EGR.
That is the reason and design. But if the engine already runs cool enough that a drop is not needed, then is the whole system needed?

The only thing exclusive to cylinder 6 with regards to the EGR is that the exhaust that is re-injected is scavenged from the exhaust manifold of cylinder 6. This scavenged gas is dumped back into the intake manifold an flows into every cylinder.
The problem with the EGR system design is that the exhaust gas gets dumped into the plenum directly over the #6 cylinder. While it's an open plenum design, the nature of it means that most (if not all) of the exhaust will go straight down the #6 cylinder.


I think the PCV system is a bigger culprit here. Put on a catch can and minimize the oil in the intake and the exhaust soot will flow right through.
I agree that the catch can is an excellent idea.
 

7schulz

 
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Ok so which vacuum lines do I need to block. I really need a pic for that one. I will check the PCV to see if it is stuck. I do think the truck runs a little high on the oil pressure gage.
 
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7schulz

 
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So not the ones circled in red but the two to the left of the blue modulator. Can I take one and just route it back on the one next to it and the same for the one on the modulator?
And the red neck guide for the paper clip is there a picture of that so I make sure I get the ECU side, and not sensor side?
 

96r50

 
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In some vehicles. Not necessarily in the 1FZ.

Plenty of people drive around with plugged or disabled EGR systems (and the EGR temp sensor not bypassed) and no CEL is thrown. Why is no CEL thrown? Because the ECU believes that the engine is in the correct operating temperature without the EGR system active.
Why not necessarily the 1FZ? Is it not simple chemistry? I would think that reducing the available oxygen in the cylinder by diluting it with inert exhaust gases should reduce the combustion temperatures, regardless of the engine.

As we all know, the EGR CELs are for insufficient or excessive flow, as measured by the EGR temperature sensor. These codes are set when the EGR temp sensor is not reading in a certain range under certain conditions. So if the EGR temp sensor is in the correct range and sending the right resistance readings to the ECU, why would there be a code? The ECU cannot "believe" anything, it only knows what the sensors are telling it.

It sounds like you're saying the ECU uses the EGR to keep the engine temperatures under control, with which I would disagree (that is the role of the rad/fan/thermostat/water pump and is monitored by the coolant temperature sensor). IIRC the only thing the ECU can do to reduce an overheat is shut off the AC compressor. It has no other method of controlling the coolant temperature that I am aware of, since the whole cooling system is mechanical/automated and uses thermostatically controlled valves (fan clutch & thermostat)


Corrolation != Causation, so I cannot say for 100% sure that the EGR system causes it, but it's certainly likely. It could be a couple of reasons.

One possibility is the varience in temps. If cylinder 6 is running significantly cooler than cylinders 1-5, then the temp difference could cause stress that could cause it.
I don't understand how cylinder 6 would run any cooler than the others?


The EGR system is disabled under heavy loads, accelleration, WOT, etc. In other words when the EGR system is disabled is when the engine will run it's hottest and be under the most strain and stress.

The EGR system is only active when you are cruising, which is when the engine is under very little stress and going to be running cool. During high speed cruising you have tons of cooling (maximum air flow) and very little load so there's no heat build up. The engine doesn't need to run cooler under those circumstances as it's already naturally running cooler than it would in comparison to driving around town, for instance.
I think the EGR is disabled under "heavy loads" so the engine can produce maximum power (yay 212 HP!) as needed. As I mentioned earlier, the inert gases limit the combustion reaction by displacing oxygen, so if the ECU wants to make more power/combustion it closes the EGR valve so the cylinders can have the maximum available oxygen content. I don't think the EGR is disabled to prevent overheating due to the recycling of hot exhaust gas into the intake.

Again, it sounds like you are tying the EGR function to the engine temperature management. I don't think the ECU makes any connection between the coolant temperature sensor and the EGR temperature sensor other than disabling the EGR until the engine is at operating temperature/closed loop/something like that!


That is the reason and design. But if the engine already runs cool enough that a drop is not needed, then is the whole system needed?
IMUnderstanding, it's not about temperature management, it is about reducing NOx emissions. The fact that reducing NOx emissions by injecting inert exhaust gases also happens to cool the temperature in the cylinder is a side effect IMO, not the goal.

The problem with the EGR system design is that the exhaust gas gets dumped into the plenum directly over the #6 cylinder. While it's an open plenum design, the nature of it means that most (if not all) of the exhaust will go straight down the #6 cylinder.
The gas is dumped in directly behind the throttle body, in the centre of the intake manifold, so it should be equally distributed to all 6 cylinders. It is no more likely to end up in cylinder 1 than 6. The crusty hole in the top centre is where the EGR gas comes in, even before the plenum opens up.



I agree that the catch can is an excellent idea.
It's nice to know we can always agree on something! :flipoff2:

:cheers:
 
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Can I take one and just route it back on the one next to it and the same for the one on the modulator?
Yup.

And the red neck guide for the paper clip is there a picture of that so I make sure I get the ECU side, and not sensor side?
Read the thread I've linked you to twice now. But I doubt you can miss it. ;)


Why not necessarily the 1FZ? Is it not simple chemistry? I would think that reducing the available oxygen in the cylinder by diluting it with inert exhaust gases should reduce the combustion temperatures, regardless of the engine.

As we all know, the EGR CELs are for insufficient or excessive flow, as measured by the EGR temperature sensor. These codes are set when the EGR temp sensor is not reading in a certain range under certain conditions. So if the EGR temp sensor is in the correct range and sending the right resistance readings to the ECU, why would there be a code? The ECU cannot "believe" anything, it only knows what the sensors are telling it.
Argh! I wrote up a nice long explanation and it got lost. So you'll have to settle for the short one.

Long story short, if you disable the EGR system but leave the EGR temp sensor hooked up you will occassionally get the CEL (I was getting it once every week or two when I was testing it). So from my personal experience the ECU reads the temps as being correct, even with the EGR system disabled, most of the time.

Because the ECU is flagging the EGR system as green, the temps must be correct for that to happen. And if the temps are correct despite the EGR system being disabled....doesn't that indicate that the EGR system is not necessary to keep the correct temps?


It sounds like you're saying the ECU uses the EGR to keep the engine temperatures under control, with which I would disagree (that is the role of the rad/fan/thermostat/water pump and is monitored by the coolant temperature sensor). IIRC the only thing the ECU can do to reduce an overheat is shut off the AC compressor. It has no other method of controlling the coolant temperature that I am aware of, since the whole cooling system is mechanical/automated and uses thermostatically controlled valves (fan clutch & thermostat)

I think the EGR is disabled under "heavy loads" so the engine can produce maximum power (yay 212 HP!) as needed. As I mentioned earlier, the inert gases limit the combustion reaction by displacing oxygen, so if the ECU wants to make more power/combustion it closes the EGR valve so the cylinders can have the maximum available oxygen content. I don't think the EGR is disabled to prevent overheating due to the recycling of hot exhaust gas into the intake.

Again, it sounds like you are tying the EGR function to the engine temperature management. I don't think the ECU makes any connection between the coolant temperature sensor and the EGR temperature sensor other than disabling the EGR until the engine is at operating temperature/closed loop/something like that!
I'm not tying the EGR to engine temps (though it is about controlling temps, see below).

My point was that the EGR system could not cause pinging or piston meltdown because when it is active is when the engine is the least likely to ping or melt a piston (short of it being turned off).

I was specifically addressing Pin Head's coment about disabling the EGR system causing massive engine failure, which simply is not true.


IMUnderstanding, it's not about temperature management, it is about reducing NOx emissions. The fact that reducing NOx emissions by injecting inert exhaust gases also happens to cool the temperature in the cylinder is a side effect IMO, not the goal.
Actually the whole point to the EGR system is to reduce temps.

From Wikipedia:

Because NOx formation progresses much faster at high temperatures, EGR reduces the amount of NOx the combustion generates. NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature.
From the FSM:

The recirculated exhaust gas lowers the combustion temperature and NOx production is reduced. Under some driving conditions, EGR gases affect driveability. Under these driving conditions, the ECM commands the VSV for EGR–cut to block the engine vacuum source to the EGR valve. Blocking the vacuum signal allows the EGR valve to close and stop recirculation of the exhaust gas to the intake manifold.
Reduce combustion temps, reduce NOx. NOx is created by high combustion temps, so the only (reasonable) way to reduce it is to reduce combustion temps.


It's nice to know we can always agree on something! :flipoff2:

:cheers:
Oh I'm sure we can find something. :p
 

96r50

 
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(Maybe we should ask a mod to move this into your EGR thread to keep it all in one place)

Argh! I wrote up a nice long explanation and it got lost. So you'll have to settle for the short one.

Long story short, if you disable the EGR system but leave the EGR temp sensor hooked up you will occassionally get the CEL (I was getting it once every week or two when I was testing it). So from my personal experience the ECU reads the temps as being correct, even with the EGR system disabled, most of the time.
Copy+paste my friend, copy+paste! It's the online save function ;):D

If you disabled the EGR and left the EGR temperature sensor in place, I would guess that you were only getting the P0401 code, true? Since (as I'm sure you know) the ECU can only set that code when you go over 50 mph for at least 3-5 minutes and the EGR temps don't exceed 100F above ambient temperatures (measured from the MAF), if you were doing strictly in-town driving it could take weeks or months for that code to appear. Obviously I wasn't there, but I would guess that the ECU wasn't reading the EGR temperatures as correct, but that it had not yet managed to do a check on the system, as you had not exceed 50 mph for 3-5 minutes. If the previous check was good (before you disabled the EGR), is it possible that it was showing that result as it was the last known condition of the EGR system?


Because the ECU is flagging the EGR system as green, the temps must be correct for that to happen. And if the temps are correct despite the EGR system being disabled....doesn't that indicate that the EGR system is not necessary to keep the correct temps?
I'm not sure what you're saying here, as I'm getting confused when you are referring to "temps". Are we talking exhaust temps as read by the EGR temp sender, or coolant/engine temps as read by the coolant temp sender, or both?


I'm not tying the EGR to engine temps (though it is about controlling temps, see below).

My point was that the EGR system could not cause pinging or piston meltdown because when it is active is when the engine is the least likely to ping or melt a piston (short of it being turned off).

I was specifically addressing Pin Head's coment about disabling the EGR system causing massive engine failure, which simply is not true.
I agree that disabling the EGR should not cause engine failure


Actually the whole point to the EGR system is to reduce temps.

From Wikipedia:

From the FSM:

Reduce combustion temps, reduce NOx. NOx is created by high combustion temps, so the only (reasonable) way to reduce it is to reduce combustion temps.
Combustion temps, yes. It sounded earlier like you were saying the EGR helped control the engine/coolant temps.


Oh I'm sure we can find something. :p
:beer:
 

Pin_Head

 
 
 
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My basic point is that it is well known that combustion temperature increases with increasingly lean air fuel mixture. This should not be confused with the engine heat that the cooling system has to deal with. If you run a really lean mixture for long enough it can lead to melting a piston, so the higher the combustion temperature, the more likely that this might happen. I didn't claim that it will always result in catastropic failure; just that it might increase the risk of it. Modern EFI engines in the US have been engineered to take advantage of the fact that the EGR cools the combustion temperature to run a leaner mixture than would otherwise burn at a safe temperature during light load cruise conditions to improve gas mileage and help meet CAFE standards. So what would happen if the engine did run lean without the EGR? We don't know and we don't know that it does run lean. It seems likely that the ECU will detect the excess O2 and enrich the mixture but this would result in worse fuel economy.

After reading the emissions section of the FSM, I don't know enough how the ECU responds a non functioning EGR to conclude that there is no potential problem. I feel reasonably confident that Toyota engineered it so as to protect the engine, but if you fool the ECU into thinking that the EGR is working rather than detecting the fault and setting the MIL, then maybe it might not work as Toyota intended. A lot of engineering went into this and it seems like an unnecessary risk to fool with it without knowing the details of how it works and how the ECU is programmed to respond under these conditions if you don't gain anything significant.
 

7schulz

 
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I found the EGR and the vacuum hose to reroute but I couldn't find the temp sensor. Where is it burried at?
 
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