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Discussion Starter #1
Hello all...as I've started to get to know these 3rd gen engines a bit...2015 2.0 6 speed hatch...I've found it to be a pretty interesting little motor. As you all know, once the intake manifold is off...you might as well do the pcv, oil catch, etc.

As I mentioned from the title, I decided to get into this car and what I found was very surprising (no pictures, too difficult to get one with no borescope). After 90K miles and some pretty hard driving over the last 30K since I bought the car...I was very disappointed when I took a look at the intake valves. It was obvious to me that no one had even taken the time to run CRC, mildly clean them at 50K, etc. So...I went to work. I would say the carbon build up was excessive and mazda has mitigated, but not solved this problem yet. Maybe the skyactiv-x...

If I'm being honest, I was one redline away from possibly sending a couple of pearl sized bits of carbon through my Catalytic converter...scary feeling when you see huge balls of carbon hanging off the edge of valve stem like that...

In short, it took me full day doing roughly 5-6 treatments of CRC, brush, pick action, and vacuum. Once I was done with the 2/4 cylinders, I rotated the engine and moved on to the 1/3. It took 2 cans of CRC to get the job done (including throttle body, IM, PCV, Oil Catch, and intake valves). Probably would have been easier to walnut blast...but I am limited to a small garage and little money.

Something about the job was very satisfying though...and I must say, this engine has been restored. I didn't realize how much the intake valves were causing the engine trouble. The things I have noted are as follows:

1. Idle is smoother than puppy fur. The idle got rough occasionally when not driving around alot...which I only do occasionally since I hit the highway everyday. I bought the car for the gas mileage...etc.
2. Low end acceleration makes me smile again.
3. Throttle response is back!!! Very little delay anymore
4. Powerband extension (the car pulls more consistently)...from 2-5K now...vs. 3-4K before the clean, etc.
5. Gas mileage bump...only 100 miles so far but +5 mpg already...

Again, my car was obviously neglected (at least from a car enthusiast perspective). However, I would highly recommend this to anyone buying a used skyactiv motor looking to restore performance around 100K.

NOW...with all that being said...this service was not necessary if I didn't know what I know about cars and have the desire to see this engine hit 300K+.

Final note, this is not a fun job--my back is killing me and I let the chemicals do most of the work. When I do it again, I'll make sure to have a headlamp too...haha.
 

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Was intake manifold removal reasonable to do... or was it hard? I hear your point about garage space and $... but folks are finding that walnut shell blast is the way to do it reasonably easily. Did you find the factory catch-can pretty mucked? What about pcv?
 

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Interesting. Let us know if you see any improvements in fuel economy. Provided you have a baseline to compare with of course.

You'll notice in the sticky above I did the same job. Yeah it sucks! However, I noticed no change despite a bit of carbon buildup. Would you mind checking my pics and giving us an idea of how bad yours was in comparison?

Also, was this car mostly city or highway driving?

I use no chemicals myself. Just regular oil changes and maintenance. I tried using the CRC valve clean directly on the valves and found it to perform worse than regular throttle body cleaner. Did almost nothing truth be told.
 

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Was intake manifold removal reasonable to do... or was it hard? I hear your point about garage space and $... but folks are finding that walnut shell blast is the way to do it reasonably easily. Did you find the factory catch-can pretty mucked? What about pcv?
It's a pretty easy job. Some bolts can be a little hard to get to, especially if you have big hands. I was able to remove mine in about 10 minutes but then I have rather small hands.
 

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When Ibought my '17 Mazda6 - one of the considerations for me, knowing it was not "dual-injected", was how comparatively easy it was to pull the manifold for a walnut shell blast. Pretty easy compared to some engines, it seems to me.
 

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Hey Thanks for these insights. I had the same issue with my 2012 ... especially the injectors where pissing not spraying. Mazda Mechanic figured it was two things to cause the injectors to foul up and the carbon build up. Ethanol and also because the car sat idle for almost a year before i bought it. Ethanol gets gummy ...long story short. I use the liqui moly fuel system cleaner or injection cleaner and now only use 91 gas (here its has no ethanol the other blends have up to 10%) If you use ethanol based gas use a stabalizer from time to time. PCV on the 2.3L is critical to change early...I changed mine when i also replaced the intake shutter vale & solenoid (got a CEL for this one). I recently flushed the rad (over due mazd asay doo it at 150K kms) with liquid moly rad flush and at the same time replaced the thermostat and upgraded the hoses to silicone. Its feels like there less load on the engine now . Your points 1-4 ..yup i feel it too... although not he MPG ..im tuned rich for the extra hp (with the mods i have on)
 

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I appreciate your insight. You know how much a concern this issue is for many modern engines. Too bad you couldn't get pictures because it would have gave a lot more weight to your post. Hopefully others will get pics soon
 

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Discussion Starter #10
Wow...tons of responses. Thanks! Yeah...no borescope, grainy crappy pics...sorry.

I feel like this car was mostly highway driving given it's amazing 42mpg at 69 mph like clock work. As far as the build up, I'd say the valves, side walls and runners had at least 1-2mm of build up...based on your pics I'd say I was double what you had. Like I said in my OP...their were chunks floating on the valve stem. That's why I went ahead and cleaned them to the extent that I did. I certainly was hoping mazda had solved this problem, however my rough idling and high rpm rattling had me a bit worried.

Catch Can and PCV from factory was spotless--i hit them with a touch of carb clean--and it seemed to help the pcv rattle a little smoother. I chose not to replace it, because it ain't broke and I've learned the hard way. The catch can had a touch of oil (dark stuff) in it--nothing major to worry about. I even reused all the gaskets. I'm telling you, I'll buy another Mazda just on the design alone for enthusiasts. I did not feel like my honda or nissan were easy to play with in comparison, especially when I added forced induction. Still think there is a huge market for a pulley driven supercharger on these puppies. 13:1 and 10 psi would just sing...might have to replace the gaskets then though :eek:

Anywho, as far as my baby...my only complaint was that it wasn't a CX-5 so I could stand up taller...:cool:

The head cleaned up really well too...surprisingly given the abuse really. I'll take good care of her now.

Finally, MPG discussions to come later. At 150 miles I'm at 33.2 combined highway/city--keeping it in the powerband while city driving and merging onto the highway. Honestly, other than 5th gear...this 6 manny is a funny puppy. Especially with that redline secret sauce. It usually takes a tank to see a stable number...I'm running premium right now just to keep it hot too burn off and flush out all the sandy carbon bits, but when I go back to 85 (Denver) I'll post an update.

Many thanks--cheers all!

??????
 

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As far as walnut blasting...yeah, already built in $10/month to cover that in 20K miles. Dealing with that many fumes is not good...I kept it ventalated, masked and glasses--but I just didn't feel comfortable watching the carbon boil off and my simple home depot mask.
 

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Discussion Starter #12
SIDE QUESTION FOR EVERYONE: Has anyone done a before and after of using the CRC spray as it was intended? I've seen folks using it online complaining of issues accelerating. Sounds bad to me???
 

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SIDE QUESTION FOR EVERYONE: Has anyone done a before and after of using the CRC spray as it was intended? I've seen folks using it online complaining of issues accelerating. Sounds bad to me???
As I've already said, I can confirm that flooding the valves with the stuff and letting it sit does nothing. You'd probably be better to mist it with water.
 

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Discussion Starter #14
Yeah, it seems the reaction slows to a halt after 10 min. I took a heat gun to one of my ports to see if it would help to "heat soak" it...no dice either. Not that a heat gun really gets it boiling, but it was definitely hot in there. Same reaction and same result as doing it cold. Truth be told, it took a lot more scraping than I anticipated based on the videos I saw prior to starting this project.
 

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I built a setup out of two sizes of tubing and. Dirty cheap sandblaster gun with a hopper on top. Probably cost me $25. But then I already have a big compressor and a shop vac....
 

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I built a setup out of two sizes of tubing and. Dirty cheap sandblaster gun with a hopper on top. Probably cost me $25. But then I already have a big compressor and a shop vac....
It was the cost of the compressor (got rid of most of my tools post divorce) vs. 2 cans of CRC that made the decision this go around. Again, I did NOT plan on doing this. In fact, I was hoping to debunk it...well, now I know.
 

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It was the cost of the compressor (got rid of most of my tools post divorce) vs. 2 cans of CRC that made the decision this go around. Again, I did NOT plan on doing this. In fact, I was hoping to debunk it...well, now I know.
Yeah I can understand the cost of compressor. A good sized one is never cheap. I get a lot of use out of mine like undercoating/rust proofing but hey that's not for everyone.

The problem with CRC is it doesn't work. To quote the old saying, there is no such thing as a wrench in a can.

I have an alternative for you. I found that although the effects are very limited, plain old throttle body cleaner is more effective. Pull the intake and let it soak for a bit. Soak up the liquid with shop towels. Next, get some small sculpting tools or dental picks and clean out the worst of it by hand. After that, you can use a shop vac to get the junk out. You can find very small but long attachments for shop vacs. That was actually part of my cleaning process.

This won't be as good as doing a walnut blast, but far better than nothing - and nothing is about what most spray cleaners do.

I did have a bit of carbon buildup (see my pics in my thread) including a good sized ball formed on the valve stems but removing all that really didn't change anything for me. Still curious for a comparison if yours is worse.

The oil catch compartment in my intake didn't really have a lot in it. More like just a thin film. I do regular oil changes and use cheap Castrol edge....sort of a synthetic I guess. My engine doesn't burn oil at all. Level does not change between changes.
 

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It won't. Fuel additives never see the intake valves, because the Skyactiv engine is direct injected, thus it never sprays fuel onto the intake valves, nor the fuel additive you linked.
It's an interference engine yes? Then it will get to them. Won't happen instantly, but it will get to them.
 
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