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· Registered
58 Posts
Good write up! I also changed my spark plugs while i was in there. I noticed that my egr was clogged! No bueno! Glad i found that when i did. I guess time will tell to see how big of a difference it will make in my ride. The whole thing didnt take long at all. Very happy i did this.

· Registered
337 Posts
I changed my plugs last weekend and decided to do the EGR mod while I was in there. I followed the instructions and put it all back together. Haven't driven it much yet but I do have a few issues that cropped up that weren't there before the plugs change / EGR mod.

1) When I first start the car the engine revs up and down a bit for about 8 seconds before it settles down and runs smooth.

2) I hear a sucking noise coming from the engine compartment when I hit the gas. I haven't been able to get in there with a stethoscope yet so see where it comes from though. Or if this sucking sound is normal once the EGR is modified.

I did NOT change the gaskets on the intake nor the throttle body when I removed them. They seemed to me to be fine so I left them (and didn't see where anyone called to swap them in the instructions). I'm not getting any codes.

Any guesses?

· Premium Member
1,323 Posts
@smashclash it sounds like you may have a vacuum leak. I would check to make sure you have all the lines hooked up to the intake manifold and intake box. I believe there is 3 hoses to the manifold.

FWIW, Nice reference to Foxtrot Uniform Charlie Kilo in your sig...I keep waiting for a new album.....


· Registered
337 Posts
Yeah, I checked them and those 3 are all hooked up. I will say I didn't recall the one line (that doesn't use a clamp) being such a tight fit. That is, it felt like I had to stretch the tube pretty far to get it on the intake nipple to hook it back up.

But just to confirm, most of you, if not all of you, do not replace the intake and TB gaskets when you changed your plugs, correct?

· Registered
337 Posts
I found the problem. Cracked air intake hose. I've duct taped it for now but ordered a replacement from amazon. Car is running fine again.

· Registered
3 Posts
Ok.........i was asked make a how to on how to do this mod. But first here is a quick explaination of what this mod if for and what it does.


the Mazda 6s from the factory has a few flaws that may be small and some that can even lead to detrimental damage to the car itself. some of these flaws and/or shortcomings can usually but not always be fixed. But of course the manufactureer wont do it.

Anyway, the design of the Mazda 6s EGR system puts the tube of the EGR directly in the middle of the intake tract. Thats bad business. Basically it blocks the airflow to the cylinders. This compounded with a decently bad design of an Intake Manifold causes 2 issues.

1. one of the 2 cylinder banks will run significantly leaner than the other. How significant are we talking here?
--it has been documented that there is about a 5%-7% difference in fuel trims between the front and rear banks.

******now on a stock motor it probably wont hurt it in the long run. but most of us owners tend to enjoy modding our rides and getting more power. and if this is left stock it could cause engine failure when dealing with power adders such as turbos, superchargers, and nitrous. again 5-7% may not sound like a lot. but that could be the difference of you keeping your 12.2 AFR in one bank......and leaning out to 13.0AFR+ in the other. then boom******

2. it blocks some airflow all together. restricted airflow=power lost

*****drive about 50mph.......stick your hand out the window. feel the pressure on your hand. you get my point*****



-8mm & 10mm sockets with accompanied rachet.
-corresponding 6" or more extension
-8mm rachet wrench(i'll explain why later)
-5/16" socket (i have an Injen CAI with hose clamps, size may vary, per intake)
-newpaper/paper towel/towel (either of the 3 will suffice)
-a hacksaw/dremel with cutting bit/ air powered wiz wheel(either of the 3 will suffice granted you have an air compressor the 3rd would be the fastest)
-pliers(needle nosed/snub nosed)
-flat tip screwdriver

****sounds like a lot but its really not****


EGR- exhaust gas recirculation
IM- intake manifold
TB- throttle body
AI- air intake


1. disconnect the neg. side of the battery 10mm (ensure that its away from the terminal and wont accidentally touch it)

2. look on the TB.........on the side closest to the firewall there is a plug with a lil red clip on it. Pull it up with your fingernail. and remove that plug from the TB.

3. disconnect the AI from the TB using the clamp closest to the TB. NOTE-actual nut size on clamp may vary from intake to intake.

****if you have a CAI there may be another Nut to loosen down by where the air filter goes into the fender(its a damper/mounting nut****

4. remove the engine cover (3 nuts)

5. remove the 3 EGR valve mounting bolts

***the bolt furthest to the right can be a PITA if using a ratchet. it can be done but i suggest using a 8mm rachet wrench***

6. remove 3 vacumm hoses from rear of IM.

***this is where the pliers and flat tip screwdriver come in handy, use them. do not try and just yank them off, where as you could snap off the nipple on the IM. the one furthest to the right can just be pulled off***

7. remove the 2 connector plugs on the front of the IM

***the other is about 6" directly to the right of this one***

8. remove 8 IM mounting bolts

***NOTE- these bolts will not come out of the IM fully. they are locked inside of it for the most part. do not attempt to remove them***

9. remove IM from engine and EGR valve. once you start picking up the IM off the motor STOP! there is one More hose under the TB you must take off. Just look under the TB and you'll see it. there are also 2 coolant lines on the TB that need to be removed. if you havent done the TB coolant Bypass, now would be a good time to do it.

***once IM is removed, besure to place the IM upside down once removed to keep dirt from getting on the seals. and place a towel or cover material of choice over it to keep debris from getting in the runners. also be sure to cover the ports on the motor as well***

***NOTE- the IM does not have to fully come out of the engine bay to do this. but it make it easier to mask the lower runners on the engine as well as keep the debris you're cutting from getting in there. remember you're are cutting metal, you wont see where all the bits and peices go. but rest assured you dont want it in you're motor....thats for sure!***

10. look at your EGR valve that is now exposed. take note that there is a point to where the tube increases in size. that point is the point you must worry about. if you cut too close to that point the EGR cooler valve will then become 2 pieces. NOT GOOD. you must cut about a thickness of 3-4 quarters before the ridge of the high point

here's a hand drawn version of what you have to do:

***once cut you have now performed the EGR Mod.

11. Put everything back together in the reverse order you took it apart. VOILA! modified/optimized EGR valve.



SECONDARY RUNNERS TIGHTENING SEQUENCE(for shits and giggles..doesnt need to be touched during this mod)


1. increased airflow to the cylinders.
2. more even air distribution.
3. possibly better Gas mileage.
4. getting a head start on having a safer motor for power adders down the road.
5. a happier motor.


approx. 30-40mins

****if doing the TB coolant bypass at the same time add another 15-20mins on it, but if you do the TB coolant Bypass, its safer to do on a cool engine****

Thanks for the explanation. Very usefully tips about EGR modification and optimization.

· Registered
22 Posts
Great write up, but I'm not sure why you're making more work than necessary.

To take the EGR off/out all you need to do is...

Remove the battery and battery trey.

Unplug the back electrical clip to the EGR.

Pull off the little hose on the EGR.

Use an adjustable wrench on the bottom nut that screws the EGR to the bottom pipe that goes to the exhaust.

Unbolt the three 8mm bolts on the EGR bracket.

Pull EGR out.

Yes, the brake fluid reservoir will be in the way but you can manipulate the EGR enough to pull it out. Trust me, I've done it.

After you mod/cut the end off, it'll be much easier to put back in.
I've also taken out the EGR with the modded pipe end, twice with the method described above.

· Registered
6 Posts
So I did this mod and now I have a VERY high-pitched whistle coming from my EGR(I think). When I disconnect the hose going to the components on the firewall(O2 sensor?) it stops and the pipe from the EGR is just sucking. I have tightened the EGR mounting bracket as much as I can and I also replaced the gasket for the EGR to the manifold, Is there something obvious I'm missing?

· Registered
23 Posts
I've done the mod, just because I had the EGR off and the cut off wheel and dremel were already out.

I need to know how to do the bypass. I know that 6crew had an awesome thing on it. But that site doesn't exist anymore. So I never got to see it. I'm 90% sure how to the bypass, just need instructions, not visual aides...

· Registered
46 Posts
I've done the mod, just because I had the EGR off and the cut off wheel and dremel were already out.

I need to know how to do the bypass. I know that 6crew had an awesome thing on it. But that site doesn't exist anymore. So I never got to see it. I'm 90% sure how to the bypass, just need instructions, not visual aides...

Sent from my SM-N950U using Tapatalk

· Registered
Mazda 6s 2007
51 Posts
I just did this mod and i cant feel any difference although i did it for one reason because i got the code p2144, which means that car egr selenoid has low cricuit or flow and that was correct cuz the sensor was burried with carbon i think only do this mod when you have codes like that saying anything about the egr valve in the 6s. Ill report if i get anything after this mod.
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