"EGR DELETE" Instructions

Afraid of head gasket issues and don't have the mechanical expertise or the wallet to have the EGR system cleaned regularly? Look into doing an EGR delete on the car. If you think your car has a misfire or pinging issue that you can feel and you think it is EGR related, a good way to diagnose the issue is to simply unplug the electrical connector going to the EGR valve. If the car starts to clear up immediately after unplugging the valve, there is your issue.
Step 1: Pop the hood.
Step 2: Look for the EGR Valve connected to the EGR cooler to the right side of the valve cover.
Step 3: Look for the electrical connector going to the EGR valve.
Step 4: Unplug the electrical connector from the EGR valve. This will give a check engine light which is what we want.
Step 5: For verification that you have done it correctly I recommend getting an obd2 scanner like one of the wireless bluetooth dongles you can get from amazon that will connect to a code reading app on your phone to verify that you get a p0403 check engine code.
Step 6: Thats it. You are done.

Notes: Don't ever do any actual mechanical modifications to the EGR system to spoof a working valve. This is a great way to get the car running the wrong mixture thinking it has EGR when it doesn't and you will blow your head gasket due to pinging. I've seen a lot of crazy ways people have done it, don't do it!

Stick to the unplugging the electrical connector and nothing more. This tells the car that the electrical circuit to the EGR valve has failed and the car now has no EGR flow into the engine anymore. The car will now run in a safer mode that is designed to run without EGR.

If you ever unplug the 12v battery, to get it back into running correctly with your EGR delete, you will have to plug the EGR valve connector back in, get the car to start the engine with the EGR valve connected, and then with the 12v CONNECTED, go back and unplug the valve again.

I'm not sure why but if you unplug the 12v battery and reconnected it with the EGR connector unplugged, the car will high idle around 1500 and shut off less. If you go back and plug the connector in and re disconnect it, it will start to idle and shut off like normal again.

Fuel economy wise I get the same low 50s in the winter and high 50s in the summer with my EGR delete. If you ever need to pass an emissions check, all you need to do is plug the valve back in, reset the code with an obd2 scan tool, and ride around and get the obd2 readiness test to pass so when you go into your emissions check it will say obd2 ready and you have no check engine codes.

We have done this with success for a couple years now on my car and friend's cars. No mechanical issues on any of these cars. No head gasket failures anymore.

 

Typically if the valve is closed it does a pretty good job at sealing off entirely. Only from what I saw on mine at least the egr valve itself does fine at sealing off.
There is a knock threshold and a long term trim for when it sees knock. Whether the knock threshold db limit is set too high or the trim amount in degrees is set too low, we will never know. Unless somebody knows how to log them. But we do know we can feel the knock and feel the car hesitate at a certain rpm, typically around 1300-2000 somewhere in there depending on car and current flow imbalances, and see there is no misfire code thrown as you're shitting yourself thinking "damn I better get rid of this car before it blows up" (we've owned many shit boxes and know what a misfire/knock feels like when its pretty serious), possibly even for thousands of miles on these cars. When it finally throws a misfire code, it seems like the car has typically already blown the head gasket on cylinder 1 or even cylinder 2 as well. Its always the farthest cylinders first.
You would think a p0401 would save you but typically the car won't always get a low egr flow code before the individual passages clog.
So the unreliability in the system to catch the issue before it blows a head gasket on cylinder 1, and the massive prevelance of blown head gaskets on these cars makes it a good idea to run without if you can.
A lot of folks say over and over again "thermal cycling" but the gen 2 runs the same bounce around coolant temps and doesn't have head gasket issues.
Toyota has also done a lot of revisions on the egr systems in the cars over time trying to remedy the issue. Larger passages, post cat egr instead of pre cat, pulling the egr into the intake into a central passage instead of from a far side making the passages more even in length, tsb's here and there, certain revisions forgoing egr etc...
They are still somewhat figuring it out as well as we are.

*The fact that we figured out you can diagnose a clogged egr knock if you are suspicious of it running rough by simply unplugging the egr valve electrical connector and it immediately clearing up is more or less what lead us down this path.

 

The egr valve and cooler clogging is usually the last thing to clog and it can adjust decently. The issue is when the manifold clogs it cannot adjust as each cylinder has a route that is uneven to the others.
Manifold clogging seems to be what the car cannot handle. Manifold egr passages are the problem with these cars above all.
Judging by toyotas larger and almost perfectly distributed post cat egr systems on the new priuses it seems they learned that from working on issues with the later revisions.
The new priuses have a central intake manifold egr entrance with much more even total egr routing to each cylinder in the hope the system will be able to calculate flow better better able to catch all egr flow related issues and increase system reliability/longevitiy.

 

Intake manifold passages