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Carbon buildup in the valves/intake isn't something that would be found in UOA right?

With the few fellas surpassing the 300k mile mark, for the majority of us with the 2.0/2.5L motors, I presume we are fine without ever never "needing" walnut cleanings.


It is a bit unfortunate that we don't really have a record of how the OP's vehicle was utilized in the first 60k miles of it's life, so is it safe to guess that it was mostly city driven? Probably right?
My conclusions after doing a clean was that yes there is carbon buildup but that it wasn't enough to make any real world difference. Other cars it is very noticeable....a good friend of mine drives a little Hyundai accent with a DI engine and oh man the carbon is bad. Lots of oil too, was like mud when I cleaned it last. He noticed a significant drop in power and fuel economy. Just to quickly experiment (didn't have much time then) we just sprayed some throttle body cleaner right onto the valves and it made an immediate difference.

Our cars aren't like that. From what I found and from what we have seen on this forum, I would suspect that for virtually all of these cars out there it isn't a problem and not worth doing anything about until the car is old enough to be scrapped anyway.

For those that it is a problem it seems that how much they drive it is the issue. All seem to be driving short trips in city. The amount of oil the engine goes through is another factor. Mine doesn't really go through any while we have a few members that need to add oil between changes. Seems it's getting into the intake. For those, I would put a catch can in. For myself, there's no point.

In short, this is a problem for a very small number.
 

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Im at 253K KMs and 2.0L engine is running better than new ... Only syn oil in it on short oil change intervals. BM is correct, those miles need to be highway and redlining it weekly to help blow that buildup from happening.

After following this thread... i did some digging to find out if there is an easy inexpensive DIY way to clean your intake valves on a direct injection engine . Looked at before and after pics (close ups of intake) with Seafoam. CRC. and couple of other products. And no they didnt put this in there gas tank. It was sprayed into the intake manifold while idling at 2500, the whole can (250ML- 350ML) in interval shots until empty. Then a 1 hour soak. Then a long drive highway speeds. The product that actually showed the best results was the Liqui Moly valve clean. Only problem, its not in aerosol form. So you need a pressure sprayer or a good vaporizer. I ordered some and will give a try once it warms up here.
 

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My conclusions after doing a clean was that yes there is carbon buildup but that it wasn't enough to make any real world difference. Other cars it is very noticeable....a good friend of mine drives a little Hyundai accent with a DI engine and oh man the carbon is bad. Lots of oil too, was like mud when I cleaned it last. He noticed a significant drop in power and fuel economy. Just to quickly experiment (didn't have much time then) we just sprayed some throttle body cleaner right onto the valves and it made an immediate difference.

Our cars aren't like that. From what I found and from what we have seen on this forum, I would suspect that for virtually all of these cars out there it isn't a problem and not worth doing anything about until the car is old enough to be scrapped anyway.

For those that it is a problem it seems that how much they drive it is the issue. All seem to be driving short trips in city. The amount of oil the engine goes through is another factor. Mine doesn't really go through any while we have a few members that need to add oil between changes. Seems it's getting into the intake. For those, I would put a catch can in. For myself, there's no point.

In short, this is a problem for a very small number.
Hey Thanks
i also looked into catch cans.... results from some testing is that it doesn't solve the problem... I think money better spent on more frequent oil changes.
 

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Hey Thanks
i also looked into catch cans.... results from some testing is that it doesn't solve the problem... I think money better spent on more frequent oil changes.
My thoughts too actually. I think it'll just improve it a little is all. Another reason I didn't bother.
 

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I obsessed over this top for a couple weeks as I didn't know the carbon build-up issue was even a thing until about 3 wks after buying my '15 Mz3. After learning as much as I could from catch cans to NOACK ratings, and chemical cleaners to walnut blasting I landed on a couple final conclusions. (Keep in mind, I am by no means an expert on any of the following; totally open to comments/corrections)

First, best as I can tell, catch cans don't seem to be worth the trouble in this application. The engine already has one, and even the best cans out there don't really seem to catch all that much. The best solution would probably be to set up a small pump that pulls a vac on the pcv system and vents to atmosphere, but the EPA would probably not like that much. Whatever the case, the junk that seems to cause the worst of the issue is the junk that comes from the crankcase via the pcv, so that leads to the next point.

Second, the quality of the oil does seem to matter, as does keeping the oil clean. The longer you wait between oil changes, the more crap gets suspended in your oil. That stuff flashes off, gets sucked thru the PCV, yada yada we all know this. Stands to reason (in my head anyhow) that the cleaner you keep your oil, and the more resistant the oil is to flashing off itself, the less junk there is to deposit in the intake. The other major source of hard deposits is oil running down the valve stems from above, which means you want to keep those valve guides in good shape. Another argument for frequent oil changes and quality oil.

Speaking of depositing... Third, I read an in-depth something or other about mazda's head design. I had read elsewhere that Mazda chooses to run the intake side of it's head a little hotter than normal, as this mitigates the build-up of the hard carbon deposits that cause issues. However, in this article, the engineer mentioned that the carbon also tends to not deposit below a certain temp as well, which I thought was kind of interesting. Hopefully that will work in my favor as my poor car gets frequent very short trips; tho people seem pretty convinced this is exactly the worst case scenario for carbon build-up. I guess we'll see. I plan to do the walnut thing at 80k miles (at 55k right now).

Ultimately, I simply decided to not obsess over it. I'm running Amsoil Sig 5w-20 (very low NOACK) and a mazda OEM filter on 5k intervals. Worst case scenario, I have to have the thing walnutted every 4 years, which really isn't that bad, if it ends up being as trouble free as most of these seem to be. Well, I guess the actual worst case scenario is that I burn out my cat or score the cylinders, but I already have enough trouble sleeping, so quiet with those shenanigans.

Just my $0.02, for what it's worth.
 

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After following this thread... i did some digging to find out if there is an easy inexpensive DIY way to clean your intake valves on a direct injection engine . Looked at before and after pics (close ups of intake) with Seafoam. CRC. and couple of other products. And no they didnt put this in there gas tank. It was sprayed into the intake manifold while idling at 2500, the whole can (250ML- 350ML) in interval shots until empty. Then a 1 hour soak. Then a long drive highway speeds. The product that actually showed the best results was the Liqui Moly valve clean. Only problem, its not in aerosol form. So you need a pressure sprayer or a good vaporizer. I ordered some and will give a try once it warms up here.
I ran the CRC GDI cleaner last week and I'll re-asses my fuel economy after this gas tank. I went from 40+MPG on the highway to 32-34 on a lucky day of all highway driving. With winter blend and my Blizzaks I barely manage to get 30. I bought the car at 33k and I'm almost to 80k now. I didn't know that the DI issues were a thing until this post. I'm going to try to clear out the carbon buildup with some more italian tune ups, and if it doesn't improve I'll find someone to walnut blast it.
 

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Discussion Starter #47
UPDATE: Drove 2K miles in a week through the mountains...Denver to Phoenix. I love the landscape, so I took the most direct route which sends you through multiple mountain passes. I believe there are 5.

I drove the car very hard on the way to AZ since I was mostly going down hill. On the way back, I went for fuel economy since I was going up hill.

I have done this trip 3 times in this car, so I have a decent amount of data to compare.

FUEL: 85-87 Octane, mostly Shell or Speedway...one tank of Chevron when I got to AZ since it was convenient.

BEFORE CARBON CLEANING ( new plugs, new tires, transmission fluid): 40-44mpg when being conservative going to AZ, 38-40 when driving aggressive. I would drive in roughly 3-4 hour intervals, resting for 15-30 min. each time.

AFTER CARBON CLEANING: 38mpg to AZ, 42 coming back. So, it seems fuel efficiency hasn't changed a bit. Same driving habits as above.

NOTES: The only noticeable difference was the cars ability to pull in a higher gear through mountain terrain. In other words, what used to require 3rd or 4th gear...only required 4th or 5th gear this go around. The engine felt great when passing as well. I could accelerate much better in higher altitudes and colder temps. Typically when it's 1-4 degrees at 10K feet, the engine can feel "choked" out a bit. This go around, I was in high wind and sub 5 degrees twice with no noticeable change to the throttle response.

CONCLUSION: If you car is losing power, a carbon cleaning can improve that. However, without dyno testing it is all MY perspective and opinion. Honestly, the new plugs could have done this. IT WILL NOT improve fuel economy at all. If anything, I've lost 1-2mpg...but again, I'm driving the car far harder than before.

In my mind, I must have needed a car project or something because this did not prove to be beneficial for what I intended it to be. As ZeroGravity mentioned in another post...Mazda must have designed oversized runners and super heating them to mitigate this problem for the life of the vehicle.

SIDE NOTE: Feels great taking her over 100 a couple of times...on accident of course;););) ? ? ?
 

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UPDATE: Drove 2K miles in a week through the mountains...Denver to Phoenix. I love the landscape, so I took the most direct route which sends you through multiple mountain passes. I believe there are 5.

I drove the car very hard on the way to AZ since I was mostly going down hill. On the way back, I went for fuel economy since I was going up hill.

I have done this trip 3 times in this car, so I have a decent amount of data to compare.

FUEL: 85-87 Octane, mostly Shell or Speedway...one tank of Chevron when I got to AZ since it was convenient.

BEFORE CARBON CLEANING ( new plugs, new tires, transmission fluid): 40-44mpg when being conservative going to AZ, 38-40 when driving aggressive. I would drive in roughly 3-4 hour intervals, resting for 15-30 min. each time.

AFTER CARBON CLEANING: 38mpg to AZ, 42 coming back. So, it seems fuel efficiency hasn't changed a bit. Same driving habits as above.

NOTES: The only noticeable difference was the cars ability to pull in a higher gear through mountain terrain. In other words, what used to require 3rd or 4th gear...only required 4th or 5th gear this go around. The engine felt great when passing as well. I could accelerate much better in higher altitudes and colder temps. Typically when it's 1-4 degrees at 10K feet, the engine can feel "choked" out a bit. This go around, I was in high wind and sub 5 degrees twice with no noticeable change to the throttle response.

CONCLUSION: If you car is losing power, a carbon cleaning can improve that. However, without dyno testing it is all MY perspective and opinion. Honestly, the new plugs could have done this. IT WILL NOT improve fuel economy at all. If anything, I've lost 1-2mpg...but again, I'm driving the car far harder than before.

In my mind, I must have needed a car project or something because this did not prove to be beneficial for what I intended it to be. As ZeroGravity mentioned in another post...Mazda must have designed oversized runners and super heating them to mitigate this problem for the life of the vehicle.

SIDE NOTE: Feels great taking her over 100 a couple of times...on accident of course;););) ? ? ?
Actually you brought up another good point there - your elevation. I'm far closer to sea level than you are (Ontario, Canada) so the air will of course be much more dense. No wonder the change wasn't noticeable for me.
 

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Wow. Too much reading. Have a 2017 Mazda 3 2.0, Automatic, Phoenix, Az.
Average mpg 34 combined.

No problems yet, preventive maintenance. Regular oil changes, air filters, ect. All by the book.
Worried about carbon build up. Going to try CRC to help prevent all these problems posted.
 

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Looks alot easier with the CRC than using a the Liqui Moly Valve cleaner (you have to spray this from a pump sprayer)
I'll have to check and see with product works better...check this link on DI cleaners comparison
 

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Looks alot easier with the CRC than using a the Liqui Moly Valve cleaner (you have to spray this from a pump sprayer)
I'll have to check and see with product works better...check this link on DI cleaners comparison
Lucas oil top end additive for the fuel seems to do the trick. one bottle is good for ten tanks to clean everythign and the effect seems to last for a long while. (More than ten tanks after)
 

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Lucas oil top end additive for the fuel seems to do the trick. one bottle is good for ten tanks to clean everythign and the effect seems to last for a long while. (More than ten tanks after)
I cannot discount ...They work ...so do many other fuel additives that clean. But with direct injection engines the fuel bypasses the intake valves .. no fuel with cleaner touches them and therefore a fuel laced with cleaner additive only runs through the injector. The intake valve get fouled by unburned fuel vapors and oil vapors being siphoned back into the intake manifold through the PCV and deposits form as a result of oil slowly seeping past the intake valve guide seals and down the valve guides because 5w & 0W are thinner and slip by and blowby an engine has due to cylinder and piston ring wear, the greater the volume of crankcase vapors that are pulled back into the engine by the PCV. So any cleaner/ cleaning is done by way of intake manifold...directly spraying a intake valve cleaning product by way of your intake (air filter box) or doing a walnut blast which requires taking apart intake and manifold to get exposure to intake valve closes.
 

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Eh, all I know is it did something to improve overall driveability, but it certainly wasn't instant, just got better with each tank till around tank 6 or so.
 

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Is there any technique involving the insertion of cleaning materials through the PCV? IE, connect a hose to the PCV system and let it suck up the cleaning solvents for the intake valves?

If the problem is that oil is being sucked onto the intake valves by the PCV system, why not use that same technique for cleaning as well.
 

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Is there any technique involving the insertion of cleaning materials through the PCV? IE, connect a hose to the PCV system and let it suck up the cleaning solvents for the intake valves?

If the problem is that oil is being sucked onto the intake valves by the PCV system, why not use that same technique for cleaning as well.
True... PCV does get clogged eventually ... Moderator can correct me ..PCV should be changed at an interval over 250K kms. You can try that way but gaining access to the PCV is more difficult than removing an airfilter and then properly aerosaling a fine mist so it coats all surfaces easily ... Pushing the product thru the PCV hosing may take long time
 

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There are plenty of products that are designed to clean the intake valves and PCV by spraying into the intake or PCV hose. The problem is that they are not very effective if at all. The chemicals have a very short exposure time to what you want to clean so they would have to be some pretty powerful stuff. That also presents a problem to the engine components. Might be effective against wet oil and muddy oil soaked soot, but in my experience this is not an issue for our engines. We tend to suffer from hardened carbon deposits. I've also found that to have no real effect to driveability, but that's another topic.

As stated here many times, cleaners in fuel will do nothing as any GDI engine such as ours bypasses the intake valves and sprays fuel right into the cylinders.

Unfortunately there is no easy fix here. As always, there is no such thing as a wrench in a can. The only way to properly clean it is to pull the intake. Pick out the large deposits and polish with walnut blast.
 

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I shall see if the liqui moly intake valve cleaner product does make an improvement (doing a second treatment this week). Only way easy way i can check is a do a 0-100KM time check compared to some past numbers. Ideal would be a have a look at the intakes with a camera or do a dyno. The way im thinking (walnut blast cost is about what...$250-300)
is take the cost of a blast and have the intake ports polished and enlarged for $400+ (hp gain 20+). LArger intake polished port may reduce eventual build up. Only old argument i see is that polished ports may reduce fuel / air velocity in lower rpm, which lowers torque, , but thats on non direct injection engine. Food for thought
 

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I shall see if the liqui moly intake valve cleaner product does make an improvement (doing a second treatment this week). Only way easy way i can check is a do a 0-100KM time check compared to some past numbers. Ideal would be a have a look at the intakes with a camera or do a dyno. The way im thinking (walnut blast cost is about what...$250-300)
is take the cost of a blast and have the intake ports polished and enlarged for $400+ (hp gain 20+). LArger intake polished port may reduce eventual build up. Only old argument i see is that polished ports may reduce fuel / air velocity in lower rpm, which lowers torque, , but thats on non direct injection engine. Food for thought
I'm always curious, but I think you'll have to do a bit more legwork if you want to prove that product works or not. Pull the intake and look at the valves prior and then do it again after a few treatments to compare. Way too many factors involved with Dyno testing. When I cleaned my valves I found that even though there was some carbon buildup, cleaning it out didn't give me any more power or fuel economy. We do know that enough carbon will reduce both power and fuel economy so I'm quite convinced that it is very dependent on how much is there. I suspect it's linked to driving type. Since I drive mostly highway, the valves are getting fully heated for a long period of time reducing the carbon.

If you have a good sized compressor that can handle sand blasting and a shop vac, walnut blasting can be done yourself very cheap and it's not difficult. A cheap sand blaster and some tubing is all that is required.
 

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I agree... using fluids to clean intake deposits may show minimal results/output. I showed most noticeable improvement when i used the liqui moly fuel system cleaner ... My philosophy is continual interval/maintenance.
 

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I agree... using fluids to clean intake deposits may show minimal results/output. I showed most noticeable improvement when i used the liqui moly fuel system cleaner ... My philosophy is continual interval/maintenance.
Ok think about this for a minute: you're using a fuel cleaner to remedy a valve carbon problem in an engine that sprays the fuel into the cylinders. That doesn't add up.

Logically, it doesn't do a thing for the carbon problem. That means that there was another problem. Plugging injector tips? This is provided that there really has been a change but I think arguing that is besides the point.

Without looking into the intake and making a comparison, no treatment for carbon can be said to work or not work. There is no basis for comparison. I'm willing to bet the farm that if you were to pull the intake you'd find similar deposits to the images I posted some time ago.
 
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