Cleaning Your EGR System
The exhaust gas recirculation (EGR for short) system present in all Mazdaspeed 3 and Mazdaspeed 6 vehicles is known to have some issues. It is present from the factory to help with NOx emissions and likes to clog, throwing a check engine light in the process. The common solution to this is to do a full EGR delete, and use an AccessPort to clear the CEL.
While likely the best solution, it is not possible for all people to do, especially if you live in an area with extensive emissions testing. If this sounds familiar, read on as I explain what the EGR system does, how to clean it, and how to ensure you will pass emissions afterward.
The EGR system does exactly what the name says; it recirculates some of the exhaust gasses back into the intake system.
Through some fancy chemistry, this reduces the total amount of NOx that comes out of your exhaust pipe. In Mazdaspeeds the system consists primarily of the EGR valve and the tube that connects the valve back to the intake manifold. Over time, the carbon present in the exhaust builds up, causing issues for the system. If the valve cannot open/close all the way or the tube gets clogged, your car will likely throw a P0401 code, for insufficient EGR flow. Aside from being another pesky CEL, a clogged system can cause rough idling, poor MPG, and slow startups.
Tools and Products Needed:
Degreaser/Carbon Cleaner – This will really help break up the stubborn carbon, making it easier to clean the EGR valve/tube. B-12 Chemtool works the best, but regular brake parts cleaner or other strong degreasers will work as well.
Picks/Scrapers – The cleaner will get the carbon softened but you will need something to scrape at it and get the pieces out.
Flexible Round Brush – The EGR tube can be cleaned by just soaking in the degreaser and picking out the big chunks but a round brush works even better. I used a straight brush but I think this flexible one will work better.
Coolant – The EGR valve has a coolant passage so you will lose most if not all of the coolant in your overflow tank. Be sure to buy OEM Mazda coolant or at least coolant with phosphate organic acids to keep your cooling system healthy.
Assorted Tools – You will need a regular assortment of sockets and hand tools for this job. The only irregular tools are a 22mm wrench (you can use an adjustable wrench) and some small needle nose pliers.
OBDII Code Reader – Okay you don’t NEED this for EGR cleaning but who doesn’t love new toys? This one is great for reading any CEL codes and seeing when you’re ready for emissions (more on that later).
Now let’s get started!
Start by removing the OE battery, battery box/tray, top mount intercooler, airbox lid, and turbo inlet pipe. Getting to the EGR valve is really the hardest part of this entire process. If you’re new to your Mazdaspeed and need some help removing any of these parts, MazdaSpeed Forums has a lot of resources if you just search for them. Be very careful when removing the small vacuum line on your turbo inlet pipe. The plastic barb likes to break off, causing all sorts of headaches down the road.
Locate & remove the EGR valve. It is the small aluminum piece with a round plastic top. Loosen the clamp on the black rubber hose and drain the coolant that will come out. You will lose about what is present in your overflow tank, catching it with a cup prevents a mess in your engine bay. Remove the electrical connector and the two bolts that hold the EGR valve to the engine and the whole valve will come free. Be sure to keep track of the gasket between it and the engine.
Remove the throttle body. You must first remove the two coolant lines that run to the TB. Clamp them closed to prevent any extra coolant leakage. Remove the four bolts, and the throttle body will come free. Once again keep track of the gasket.
Remove the EGR tube. There are two bolts located by where the EGR valve was removed. Another gasket located here. Trace the metal tube back to the front of the engine and remove the large 22mm nut. You may need some penetrating fluid to help loosen this nut. The EGR tube then pulls out of the intake manifold.
Start cleaning by using a pick to remove some of the carbon from where you removed the EGR tube. There’s a bunch of gunk in there but it’s not easy to clean so do what you can.
Spray some of your degreaser inside the EGR tube and let sit while to start loosening up the carbon buildup while you clean the EGR valve.
Disassemble the EGR valve. Remove the four screws from the plastic section. The two halves should separate. These screws strip extremely easily, use care to not damage them and be sure to keep track of the gasket.
You will now have access to a plunger. This is what opens and closes the EGR valve. Push it to help you clean around the valve. Use the picks, degreaser, and whatever else you need to remove as much carbon as you can. Focus especially on the areas around the valve. Ensure it has smooth operation and can fully open and close. Take your time here.
Using the round brush, degreaser, and picks, clean the EGR tube as best as you can. I found the majority of the carbon was located toward the end with the 22mm nut. Take your time, once again, you don’t want to have to redo this.
Reassemble everything. Ensure you reconnect all hoses, reconnect all electrical connectors, use all gaskets, and tighten all bolts. Add coolant to your reservoir until you reach the max line.
You should now have a squeaky clean EGR system! Start up the car and check for any leaks or strange noises.
Now if you’re like me and had to clean the EGR system for emissions, you will need to complete a “drive cycle” to pass. All the sensors for the emissions system have to run tests to ensure that they are operating correctly. Since you had the battery unplugged, the sensors have basically reset and need to run all of the tests again. In most states, there is a limit to how many sensors can read “not ready” and still pass emissions. Guidelines to reset most if not all of the sensors are as follows (sourced from MSF):
Before you start to be sure you have: no CELs, fuel level between 15-85%, all accessories off, cold engine.
Start and idle for 5 minutes.
Rev engine in neutral to 2300-2700 RPM for 15 seconds.
Rev engine in neutral to 3800-4200 RPM for 15 seconds.
Idle engine for 20 seconds.
Accelerate to 52-55 MPH, maintain speed in 6th gear for 1.5 minutes.
Decelerate to 15 MPH, drive for 13 minutes at speeds between 15 and 35 MPH.
Drive at 25MPH for 50 seconds.
This order of steps activated all but one of my sensors, meaning that in Washington State I was able to pass emissions in my 2007 Mazdaspeed 6.
Hopefully, this will help out a few of you that are stuck with an EGR system. This procedure saves a few hundred dollars over replacing the valve, making that next modification happen just a little bit sooner!
If you have any additional tips or tricks be sure to share them in the comments, we’d love to hear your experiences!