1fz-fe EGR disable ?

[d0ubledown]

im no EGR expert, but im in the same camp as ebag and semil. why? because i've had the P0401 for the last few years. thought about adding the resistor mod, or even going all out and replacing the lines and VSV which is most likely the culprit after all my testing, but ive grown so fond of the warm glow of the CEL...it replaces the D light that seems to have died

but seriously. its been at least 35K+ miles, no issues. engine temps seem normal from 184-190 in our cold weather. gets up to 195 in the hot weather with AC on. power is strong throughout the tach. it has a barely noticable stumble at idle, but what 80 doesnt. gets an average of 13.3mpg for city/hwy combined. and thats with 100# tires/rims. no it wont pass smog.

those kinds of results that people have with disabled/non functioning EGR's should be enough to say that no, it wont cause any damage. hell, ive read posts where even people that have fully overhaulled their egr system are still throwing P0401's.

i think the rest of the world that runs sans EGR and dont report HG failures is something to look at. id even wager that all reported HG failures all had full functioning EGRs. if so, then that should be some sort of measurable factor of the poor implementation of the EGR on the NA spec 1FZ.

looking at the the way the EGR was implemented on the 1FZ seems like such an aftermarket afterthought. really? did the EGR tube need to be so close to the main engine wiring harness? really? did the VSV for EGR need to be under the intake plenum with a hokey port that passes through the intake runners for 5 & 6? why is it the VSV for egr always fails, but the other VSV (for fuel i think?)never seems to have any problems?

however...my windows dont seem to wind up as fast as they should. maybe its the EGR? could someone please prove to me that it cant be the EGR since most of the arguments against deleting the EGR in the 1FZ cannot provide any evidence that backs up their claims that it will cause damage to the engine...

to my understanding the main and only reason for the EGR is to reduce emissions. so if it not there, or it is malfunctioning...only harm that it should have is more emissions...no? or is that too simple of a theory and im just grasping straws?

 

[rolliges]

Funny how we love our over-engineered 80s until it involves a system we dont fully understand then it's an afterthought!?!?

The EGR system is integrated into our US fuel mixture. Our ECU is programmed to work with a functioning EGR system.

Take your chances at your own peril. If you're undecided look for info outside of Mud with an open mind.

 

[semlin]

Funny how we love our over-engineered 80s until it involves a system we dont fully understand then it's an afterthought!?!?

The EGR system is integrated into our US fuel mixture. Our ECU is programmed to work with a functioning EGR system.

Take your chances at your own peril. If you're undecided look for info outside of Mud with an open mind.

sorry but you need to back that up with some actual reasoning instead of just blasting off assertions like that.

our ecu is programmed to alter fuel delivery until the correct stochiamatic mixture is reported by the o2 sensor. it is also programmed to map out and remember the amount of fuel that works best with the particular vehicle as it happens to be tuned. it thus adjusts and custom tunes the fuel flow to take into account variations in air flow.

our ecu has enough flexibility for toyota to believe it can adjust to the increased airflow of a factory supported supercharger.

our ecu has enough flexibility that toyota believed it was not necessary to warn customers if the egr system was not working in its 1993 model so it did not include an egr temp sensor except where required by law in california. this probably saved toyota about $5 a vehicle. it seems unlikely they would cut a corner like that if the risk was in any way significant.

for those who believe the 1993+ ecu may have been upgraded to take into account the egr flow, it seems unlikely to me that the flexibility of the original programming would be reduced. egr failure was still completely foreseeable. plus, the later ecu's do a better job of regulating air flow with a supercharger, which suggests they are more flexible generally than the 93 ecu, not less so.

 

[d0ubledown]

The EGR system is integrated into our US fuel mixture. Our ECU is programmed to work with a functioning EGR system.

'the' meaning the 1fz? or all egr in general? if you're referring to the 1fz, then please state your source. because if it's true, then why does mine, ebag's, bear80's and countless others' 80 series still continue to function flawlessy with no functioning egr system?

back up with facts, tech bulletins, or fsm quotes...or keep an open mind. otherwise you're just grasping at straws..

 

[bmwjnky]

I didn't read all 5 pages of posts but I thought I'd add my .02 to this. After coming to the conclusion that my VSV is causing my code 71 since everything else tests good I decided to disable my EGR. Right off the bat no more CEL but after about a week and a half of daily driving the idle was about 25-50 RPM higher, the idle was smoother and over all the engine felt smoother with a little bit better power. My commute is the same everyday, gas brand and grade are the same so the only thing I can think of is the EGR being disabled helped. No noticeable change in fuel mileage but I stopped keeping track after the first month or so of owning my cruiser.

 

[Ebag333]

The EGR system is integrated into our US fuel mixture. Our ECU is programmed to work with a functioning EGR system.

Take your chances at your own peril. If you're undecided look for info outside of Mud with an open mind.

What Semlin said.

The ECU doesn't give a lick about the EGR system for fuel mixture. They have nothing to do with each other.

The fact is, the ECU has no way of measuring how much exhaust the EGR system is introducing into the engine. There is no MAF attached to it, only a temp sensor which tells you nothing about how much flow you have. The EGR system is essentially introducing unmetered air into the system, which means it's bypassing one of the primary systems for determining how much fuel to put into the engine (MAF).

O2 and MAF are the two big factors for fuel, along with the fuel maps built into the ECU. The EGR system isn't part of that.

And that's all in the FSM. Please show me where the FSM states that it uses the EGR system to change the fuel map.

 

[mahalkita]

The 1FZ came originally with a carburetor and a very simple intake and NO EGR! For countries like the U.S. all the emissions cr*p was added on, it has certainly no purpose cooling the engine etc. and it will certainly run without EGR, in fact it will run more efficient and without all the soot and dirt coming back into the intake.
I have driven that combo in Saudi Arabia when it came out, ambient temps where much warmer than Arizona in the summer - no extra engine cooling by the EGR included! Worked like a charm with a carb and no EGR, same power as EFI has now. No problem with idle etc. great driveability and same fuel consumption as others are getting now with EFI / EGR. Just simple and very reliable performance - if you go out in the desert which is more than 3 times bigger than Texas you don't want to break down on overheating or some cr*p in the engine bay which is not necessary failing - you might DIE otherwise!
People forget that this truck was developed to survive the most brutal climate extremes on earth - mostly HEAT! Its not a shopping cruiser like the 100 or 200 series!
If the engine needed egr to run cooler it would certainly had one in the Middle East or Africa - but it did not have one. Its not needed, not beneficial, not even to nature because it wastes more fuel making the truck running more inefficient. That little reduction of Nox doesn't compensate for the long term problems caused by all the dirt in the intake for hundreds of thousands of miles....

 

[kidglove13]

The EGR is purely for emissions and has no relation to fuel curve
When I disabled mine I noticed no difference what so ever, it was more of keeping that crap out of the intake and to stop blowing hot exhaust gases into the cylinder #6 area.

 

[Pin_Head]

to my understanding the main and only reason for the EGR is to reduce emissions. so if it not there, or it is malfunctioning...only harm that it should have is more emissions...no? or is that too simple of a theory and im just grasping straws?

That was the 1974-1980s view of EGRs.

Newer EGR systems improve fuel economy in addition to reducing NOx. They improve fuel economy two ways: 1) it allows a leaner mixture to be burned at cruise conditions without having an excessively high combustion temperature. 2) it lowers manifold vacuum under partial throttle cruise conditions, so the engine does not have as large of a "pumping loss".

Please show me where the FSM states that it uses the EGR system to change the fuel map.

Please show me where the FSM states that it does not use the EGR system to change the fuel map.

 

[Ebag333]

Please show me where the FSM states that it does not use the EGR system to change the fuel map.

I guess if the FSM never states that it does not use the EGR system to change fuel maps, that must mean it does use the EGR system to change fuel maps.

It does not say that it doesn't use the gravitational force of the moon to improve fuel economy. So I guess we have a moon powered truck.


It's impossible to prove a negative. Along the lines of "prove you don't eat kittens for breakfast" or "have you stopped beating your wife."

The FSM is very clear on how it manages fuel. There are large sections of it dedicated to this, specifically on the O2 sensors and MAF. Seems like that'd be slightly odd if the EGR system was used to manage fuel...yet the FSM doesn't mention it, yes?

 

[semlin]

That was the 1974-1980s view of EGRs.

Newer EGR systems improve fuel economy in addition to reducing NOx. They improve fuel economy two ways: 1) it allows a leaner mixture to be burned at cruise conditions without having an excessively high combustion temperature. 2) it lowers manifold vacuum under partial throttle cruise conditions, so the engine does not have as large of a "pumping loss".

that may be true on some newer vehicles but not in relation to the 80.

a. the 80 series egr does not engage at cruise conditions

b. the 80 series manifolds were also used in markets with no egr installed, and therefore were not designed to require any input from the egr to maintain proper vacuum pressure.

c. the fsm describes the egr system as an emissions control device. it makes no mention of the purposes you describe. mr. t is pretty thorough.

d. even if you were correct, the ecu would retard the timing if it detected knocking.

 

[Pin_Head]

It's impossible to prove a negative.

Exactly. Absence of evidence is not evidence of absence.

 

[mahalkita]

That was the 1974-1980s view of EGRs.

Newer EGR systems improve fuel economy in addition to reducing NOx. They improve fuel economy two ways: 1) it allows a leaner mixture to be burned at cruise conditions without having an excessively high combustion temperature. 2) it lowers manifold vacuum under partial throttle cruise conditions, so the engine does not have as large of a "pumping loss".
Please show me where the FSM states that it does not use the EGR system to change the fuel map.

I think you misunderstand a semi sophisticated tractor engine which runs on anything but pure water anywhere in the world with a modern 2.0 ltr. ricer engine.....

AND - there is nothing new or special on this EGR implementation, it just opens a valve, letting the hot dirt back in once clean intake. It was a add on for the poor first world we live in. How much more fuel you think the fuel management has to inject into the intake over the many years (a almost 20 year old design) to pass by all the dirt accumulated and clogging up everything including the EGR itself?

 

[kirkm76]

The EGR valve has been federally mandated since 1968 if I am correct. I am confident on my 93 it is an emission only device. I have no check engine light since ditching it. As I said though, mine is a Federal 93 so the ECU has no clue what the EGR is doing (or not doing).

 

[Ebag333]

a. the 80 series egr does not engage at cruise conditions

Actually, that's the only time that the EGR operates.

Exactly. Absence of evidence is not evidence of absence.

If you believe that...well..then you're screen name fits.

There is zero documentation that the EGR system has anything to do with fuel mapping. If you believe that means it has something to do with it, then you're an idiot. You might as well believe that paint color changes fuel mapping, since there's no documentation that it does not.

 

[Pin_Head]

If you believe that...well..then you're screen name fits.

There is zero documentation that the EGR system has anything to do with fuel mapping. If you believe that means it has something to do with it, then you're an idiot. You might as well believe that paint color changes fuel mapping, since there's no documentation that it does not.

Ooooh, smack! Kinda personal too.


If the EGR system has nothing to do with fuel, then why did Toyota include the EGR temperature sensor check in the FSM chapter on sequential fuel injection (SFI) on page SF63? I guess either Toyota thought it was important to the fuel system or they just put stuff in random places in the FSM. Now you can show me the evidence that there is no relationship of the EGR to the fuel system.

 

[Ebag333]

Ooooh, smack! Kinda personal too.


If the EGR system has nothing to do with fuel, then why did Toyota include the EGR temperature sensor check in the FSM chapter on sequential fuel injection (SFI) on page SF63? I guess either Toyota thought it was important to the fuel system or they just put stuff in random places in the FSM. Now you can show me the evidence that there is no relationship of the EGR to the fuel system.

Well, it's physically near the SFI system. So in that respect it makes sense to put it there.

Just because it's in a section in the FSM doesn't mean it's connected. If a cat has kittens in an oven, they aren't called biscuits.

There is zero mention of fuel management in regards to the EGR system. (Even in what you posted!) So there's the evidence that there is no relationship of the EGR to the fuel system...the lack of evidence.


Now show me the evidence that paint code doesn't effect fuel map. I've always thought dark green 80's were the fastest, and white 80's the slowest.

 

[rolliges]

This is from Toyota Motor Sales, USA Inc.
EMISSIONS SUB SYSTEM - Exhaust Gas Recirculation.
...
"EGR Impact on the Engine Control System
The ECM considers the EGR system an integral part of the entire Engine Control System (ECS). Therefore, the ECM is capable of neutralizing the negative performance aspects of EGR by programming additional spark advance and decreased fuel injection during periods of high EGR flow. By integrating fuel and spark control with the EGR metering system, engine performance and fuel economy can actually be enhanced when the EGR system is functioning as designed. "

 

[Ebag333]

This is from Toyota Motor Sales, USA Inc.
EMISSIONS SUB SYSTEM - Exhaust Gas Recirculation.
...
"EGR Impact on the Engine Control System
The ECM considers the EGR system an integral part of the entire Engine Control System (ECS). Therefore, the ECM is capable of neutralizing the negative performance aspects of EGR by programming additional spark advance and decreased fuel injection during periods of high EGR flow. By integrating fuel and spark control with the EGR metering system, engine performance and fuel economy can actually be enhanced when the EGR system is functioning as designed. "

So where did you find that in the FSM? Reference please.

If it's just a generic statement, then it's not applicable to 80's specifically.

New EGR systems are different than what is found on an 80. In new cars, there is little to no reason to disable them as they are interconnected and the ECU does change the fuel mapping based on the EGR status.

There is zero evidence of this, and in fact the ECU has only the most rudimentary view into whether the EGR system is functioning or not.

Modern systems utilizing electronic engine control computers, multiple control inputs, and servo-driven EGR valves typically improve performance/efficiency with no impact on drivability.

We don't have multiple control inputs, servo driven EGR valves, or most anything else that comes on modern EGR systems. Our's is an entirely mechanical and quite stupid EGR system, which is why you can bypass the temp sensor entirely (or have the system plug up, or disable it) and drive hundreds to thousands of miles without the ECU throwing a code, because it thinks the system is operating perfectly fine.

 

[rolliges]

This is from Toyota Motor Sales, USA Inc.
EMISSIONS SUB SYSTEM - Exhaust Gas Recirculation.

"Exhaust Gas Recirculation System
The Exhaust Gas Recirculation System (EGR) is designed the reduce the amount of Oxides of Nitrogen (NOx) created by the engine during operating periods that usually result in high combustion temperatures. NOx is formed in high concentrations whenever combustion temperatures exceed about 2500'F.

The EGR system reduces NOx production by recirculating small amounts of exhaust gases into the intake manifold where it mixes with the incoming air/fuel charge. By diluting the air/fuel mixture under these conditions, peak combustion temperatures and pressures are reduced, resulting in an overall reduction of NOx output. Generally speaking, EGR flow should match the following operating conditions:

High EGR Flow is necessary during cruising and mid-range acceleration, when combustion temperatures are typically very high.
Low EGR Flow is needed during low speed and light load conditions.
No EGR Flow should occur when EGR operation could adversely affect engine operating efficiency or vehicle drivability (engine warm up idle, wide open throttle, etc.)."