A lot, if not all the information you listed is hard to use because they're all constantly changing real-time values that also depend on other real-time parameters.

Throttle position controls what the MAF would be, the MAF and O2 sensors determine whether or not the car is close to AFR/lambda... which alters the trims.

And trying to grasp all that data at the same time is near impossible as by the time you've seen what one data point is, the rest have changed by the time you look at them. Especially when you're supposedly driving.

What you really need is a logger. So that you can see what all the values are at the same point in time.

~~~~~

Does the RPM "dip" occur if you just sitting in park/neutral?

 

To: Thread starter Fujisawa and others here:

Instead of starting a new Thread--

I would like to get some advice/input regarding the attached photo of the butterfly valve on my 2015 FIT with 52K miles.

This photo was taken by the Honda dealer's service advisor in the normal course of regular maintenance last week.
He said that they are noticing carbon buildup on Honda Engines on various makes including FIT and Accord, some with substantial buildup on units that are only 1 or 2 years old and with less than 25K miles. He said that when they present the photos to new vehicle owners, they are not happy that the cost to remedy this is not covered by Warranty but the dealership does not know what else to do. They are documenting their findings for their records and Honda he says. He said that dealerships Toyota end has also inspected the valves on various models and years and has not seen this issue at all with their engines, just the Hondas.

The service advisor recommended, but did not urge cleaning the throttle body, fuel injectors, and de-carbonize the engine.

I have not noticed a performance issue with my FIT and the service advisor says that performing the above work will not improve the engine or car performance at all--it will just keep the carbon from spreading which will require more extensive cleaning in the future. No other benefit to cleaning the valves he says.

Fujisawa in Boston posted a photo of his similar valve and it looks clean at 40K.

Why is mine so dirty? Could it be the special fuel blend in California is causing this. I use Chevron 100% of the time usually 92, but lately 87 due to the oppressive costs of fuel here. Chevron is not in the East Coast? but is known to be a top fuel out West? No?

I would appreciate some input on:

1) Should I clean the throttle body, fuel injectors, and de-carbonize the engine at this point as the Dealer Service Advisor recommends?
2) Is there another way to clean this by putting something in the tank that would be effective?
3) Has anyone else here seen this type of Carbon on their Valves or is it just me?

Thank you all in advance for your time.

My Honda FIT Valve at 52K miles. Photographed by Honda Dealer June 2019.

 

If that is indeed your ThrottleBody it is a bit dirty (it is possibly a "stock photo" lol). The edges have some carbon so it butterfly does not close perfectly, so at idle a bit too much air goes to the engine and the mapping will not be optimal throughout the range. Maybe idle might be slightly rougher, or power/mileage might drop slightly. IME, cleaning a throttle body with that level of grime provides makes engine run smoother and quieter so is worth the effort.

*** You can clean it with your girlfriend's teeshirt and a $5 bottle of special "throttle body cleaner" in a couple of minutes.

*** Not sure how you prevent grime on throttle body on a car with 50k miles. Keep up with oil/filter changes. Change air filter periodically. Use high quality gasoline.

I haven't read much about gen 2 FITs at 50k miles with carbon issues on the intake valves. That can be a problem on cars with only "direct injection" as the fuel does not spray down the valves.

*** Good quality fuel and driving on the highway for a while every week can help. Also you might very gently push the RPMs up to 5k for a few minutes which might help clean valves (you don't need to go above speed limit just use a lower gear when nobody else is on the road).

 

1) Should I clean the throttle body, fuel injectors, and de-carbonize the engine at this point as the Dealer Service Advisor recommends?
A: Cleaning the Throttle Body wouldn't hurt. Its not very invasive and a procedure can be provided at your request

2) Is there another way to clean this by putting something in the tank that would be effective?
A: Injectors and Valves can benefit from fuel additives, but Chevron gas already has an excellent additive in it. This is opinion based on personal experience: fuel is pretty easy to treat and clean, since you've been running good gas and your vehicle is performing well, you don't need to worry about the injectors.

If you decided to truly clean and inspect the injectors they would need to be removed.
Valves also have to be removed to be properly cleaned. Requires removal of the cylinder head.

3) Has anyone else here seen this type of Carbon on their Valves or is it just me?
A: Plenty of folks have acknowledged this issue, if you call it that. Carbon on the face of the throttle plate is the result of crankcase ventilation. Someone may chime in with other elements that could cause it, can't think of any at the moment. You could have a compression test done to approximate the amount of blow-by gasses (fumes from combustion in the cylinders that bypasses the piston rings). That could communicate whether your car is having an above average amount of carbon, fuel, getting to circulate back to your throttle body. Its a pretty simple test whether you pay for it or do it yourself.
besides that, you could invest in means to filter your EGR... Thats all i got for the time. Have a good'n
​​​​​​QUICK EDIT: Having gook there on your throttle plate can affect idle and performance by restricting the airway, which is already fairly small while off throttle. Your car's computer will recognize this and adjust the air/fuel ratio accordingly using its array of sensors. Will still run smooth, but it's one of those things.. you hop in an older car and it just dont feel as zippy as a new one. This is one of many reasons why, but it's easily fixed

 

With a 2015+ model, you are going to have new and better problems (congratulations!) than you see described above. While there's lots of good info above, I'm not sure how likely it is to apply to you. For example, all the GE complaints about plugs and coils and coals ... None of that happens in the GKs. Different engine in many ways.

You will find plenty of common problems in other threads for the GK though. Carbon buildup in the valves due to direct injection, and the TB due to some oddity in the pcv setup. At the relatively low miles here (~50k) the GE is starting to have valve clearance problems the GK may never have, while the GKs are having bumpers fall off and trying to use their own oil as a fuel additive...

 

Thank you to Pyts, Fiting, and Fujisawa for your excellent and helpful responses.

I am realizing now with Fujisawa's response that I inadvertently posted in the 2nd Generation FIT forum when I intended that it be in the 3rd Gen section. I thought that the engine picture Fujisawa posted was a GK because it had only 40K miles on it, but he has a GE. I used to have a 2009 FIT GE until a Range Rover crushed it and replaced it with a 2015 FIT I liked the FIT so much.

I may re-post my issue in 3rd Gen FIT section in order to capture those owners that have this problem.

The dealer is telling me that it's going to cost 100's of dollars to fix this, it will not stop the carbon from accumulating again, and I am aggrieved at that for a car that is supposed to be low maintenance.

 

2015 Honda Fit has direct injection.

On some direct injection cars, Intake valves may not be cleaned by fuel so carbon builds up and can be a problem at relatively low miles. Our cars are all older so I have no "direct" experience lol.

 

Same boat! But I feel that we've provided appropriate information nonetheless. Techron in chevron is on par with seafoam or any of the others. It might be time for someone to send samples to FOI Labs for analysis. Stupid injury has me lazy as hell.
Nothings fun when you stand crooked.

Injectors should be getting enough detergent through 'em to be fine at that mileage, spark plugs should be good enough to make a nice bang and create enough heat to avoid carbon fouling. Valves are the only tricky part. I must say, this is a fun topic! I'm more familiar with carbs than DI and never considered this issue.. still, a compression test would put your mind at ease. These things shouldnt require maintenance..

We have a common enemy in regards to grime in the throttle body. I need to check again, but I think my T-REV has significantly reduced/prevented gook from getting up there.. thats part of its jobber anyways. A catch can could also serve. Less junk going into the intake, less at the throttle body, less on the valves. We high five and move on.

Check out

 

The issue with DI as I understand it is that there's no longer fuel being sprayed on the back of the intake valve. So over time, a tiny bit of cylinder gas collects on the back - that or the oil from the vapor pulled in by the pcv (which is the only thing causing that TB gunk btw).

Looked like you had access to the TB so it's easy enough to clean while you are there, the front side of it anyway. Don't need to pay dealer for that.

My understanding is there's something you can spray in periodically that will help clean the back side of the valves. It won't clean valves with 100k of coal on them but it will help extend the life. You need to look that up as I am not super familiar. In all cases, don't spray anything except air in BEFORE the MAF sensor as its designed to live in a clean condition just after the filter.

I agree these developments are disappointing.

I hadn't even heard of PCV before these GKs started making noise about problems earlier this year ....! Apparently even Honda didn't think about the issue..

 

Also for clarify, when I say "valves" I refer to cylinder intake or exit valves. The throttle plate is indeed a type of butterfly valve isn't it, but I do not call that a "valve" when discussing an engine.