Hello, dear Fit freaks! I hope You all doing well today.

I have an orange 2018 Honda Fit Sport with CVT, that I bought from auctions in USA and brought to AZE in 2019. The back and trunk area were destroyed in an accident, but it affected only the cost, believe me. So the deal was nice, because odometer showed around 5000 miles. So it's a new car, with minimal damage and no problems at all.

Now to the problem itself. The year is 2021. One day I started the car in the morning as usual and it showed me 4 dashboard lights!!! These were:
1) Check Engine light
2) VSA indicator
3) EPS (electric power steering) indicator
4) TPMS indicator
And the car behaved weirdly. My steering wheel felt like a toy, it was much softer and more easy to turn. Prior to that I started noticing, that my my fuel economy gradually falls, consumption rises, MPGs are lowering (I'm not sure, I felt like that) and the car stutters very gently on cold starts and at idle (2000-1000 RPM). I went to the Honda dealer, where my car was diagnosed and they said, that I have a misfiring cylinder, and It is probably due to a clogged or even failing fuel injector. And because they are GDI, there is no option in Baku to clean them, and I have to change injectors, which are not available here, so I need to order them from USA, which can take ages to deliver aaaand it costs too much (look up USD to AZN).

My relative's mechanic's diagnostics said pretty much the same, but he added that I have EPS and ABS errors as well, but I dismissed it, as it is probably errors ECU showed as part of the main issue. He deleted the errors and added that it has happened probably because of the fuel I used since the car came here. Let me tell you about that:

I was feeding my girl the AI-92 which is a post-soviet analog of low octane (definitely lower than 87) gas. It is manufactured here in Azerbaijan, it is cheap, but it has god knows what inside: I mean EVERYTHING THAT SHOULD NOT BE IN A GASOLINE IS THERE... It is 78 or smth, they add these additives, so the octane count becomes higher. We also have A-95 (premium) and A-98 (super) which is gasoline imported from EU. It is much better, but it is very expensive. But I have no other choice, so I am now only refueling with A-95 (US Octane 87 and higher, like in the manual).

So what I did was:
1) I switched to A-95 EU premium gasoline and she doesn't stutter anymore, the RPM arrow is not dancing on cold starts.
2) I used octane booster and ordinary injector cleaner from Liqui Moly (my mistake, I used LIQUI MOLY GDI INJEKTION REINIGER PRO LINE 600 miles later)
3) I started using econ mode and driving less aggressively
~ 500 miles later...
4) I bought a OBDII bluetooth device, diagnosed the car several times myself, but it now shows no errors at all, only 2 or 3 misfires for the last cycle (which isn't bad right? )
Results:
Weeelll, I think the problem is mostly gone, but I used the REQUIRED GDI INJECTOR CLEANER today, and I am waiting for its effects to take place. The car stopped stuttering or shaking, but the fuel consumption I THINK is really bad... I don't know it shows 25-26 in city (we have traffic jams, yes) maximum 28 with econ ON. But I might be paranoid, as for the last 2 months I've been going up the hills 3 times a week, and using the car more. Via OBDII it showed 22-25 MPG on a short trip. ODOMETER TODAY: 16660 miles

I researched this topic very thoroughly, and these 4 lights most likely referred to bad injectors (via misfires). Other variants, that can cause fuel overconsumption, that I've heard or seen:
1) Clogged fuel pump filter
2) MAF sensor dirty, air system not registering enough air, air filter clogged
3) Dirty spark plugs
4) Sensor failures
5) Tire pressure low
6) I'm just paranoid, my MPG is okay...

 

Welcome. The GK5 engine seems particularly susceptible to carbon buildup early on. We recently had a post from someone with 11.5 K miles with excess carbon buildup - completely fouled cylinder head, injectors, etc. Repaired by Honda under warranty, but this shouldn't happen at 11.5K miles, much less at all.

I've been recommending top tier fuel only as a result. You don't want carbon buildup on these engines at any cost. The thinking is that the added detergents help prevent the carbon from becoming a problem.

If you've had difficulty sourcing decent fuel in your area, that could certainly lead to excess carbon, which could be the source of all this.

Outside of OBDII codes, you could take one of the plugs out and have a peek through a scope at the cylinder walls. That'll tell you whether the carbon buildup is enough to start causing problems, because if it's heavy there, it's heavy in the injectors too.

I don't know of any reliable ways to rid that carbon from the injector / rail system. This is where things start getting expensive. Typically one cylinder will start throwing codes, and then eventually all do. So you're left replacing the entire injector / rail system, typically $2-3 K in the US.

This is why I no longer recommend the GK5 in any form. It's not worth taking a gamble on these engines. We already know they have problems, and not just late-onset problems. These problems are surfacing very early on.

 

WOW!

Actually thanks a lot for the answer, I really appreciate that.

I think injector cleaner should do the job. Liqui Moly Pro line stuff should be really powerful, to clean this mess at least in the fuel system. And I'm going to add it in my tank every 5000 km as advised on the can. Also it will be logical to use octane boosters with every 2nd refueling? Any other additives, You could advise, to prevent carbon buildup?

I will definitely check the spark plugs themselves and will peek inside all 4 combustion chambers!

Also, have you heard about that method of decarbonizing or cleaning the whole system with hydrogen aka "Brown gas"? It is very popular here in post-soviet states as well as Russia. I know for a fact that that is a SCAM, because you get rid of the soot in the engine but then it immediately builds up again. But if it really cleans the carbon buildup, maybe it could be helpful with our GK5s, what do you think?

 

Rather than additives, my recommendation is to get the best quality fuel you can get as a way of avoiding problems down the road. If that's not possible, I don't know how well any additive will work, but you can try whatever you want.

The injector / rail design on all GK5s - even the very latest models - is suspect. If Honda had worked out all the issues since their TSB for all 2015 and early 2016 models that said yeah, we know about the bad injectors and will replace but only under warranty, we wouldn't be hearing about problems in the very latest models because it would have been addressed at the midcycle refresh. But here we are in 2021. Honda knows about this but no doubt would rather sell you a set of injectors and the labor involved instead of actually improving the design, but hey, what do I know.

Otherwise, anyone looking at a GK5, forget it. Look at a vehicle without major injector / rail issues.

 

The irony of the situation is that my country - Azerbaijan has the biggest oil industry in the ex.USSR. 80% of our economy is oil. Our oil is not so abundant, but the quality is top-tier. Believe me, I have several oil-related chemists-specialists and old scientists in my family.... yet the quality of gasoline here is just SH@T! Literally. It's like someone has vomited into your tank... I just learned that "european" AI-95 that we have is actually european A-90! They import it here, then some corrupt officials mix it with 78 and add additives to boost the octane count, while stealing 10% of all imported petrol. I like how Georgia has better gas at AZERI GAS STATIONS!!! It's like if Shell sold better gas in Mexico, while cheating and selling piss in US.

Anyway. There is no good quality fuel here... sad(

 

+1
Without finding and sticking with a reputable quality fuel (then diagnosing your issues), you are basically throwing random parts/solvents at your problem.
At that point it's anyone's guess as to what the issue(s) are.

Considering your issue with finding reputable fuel, if I were in your position I'd sell the Fit and purchase an older vehicle that runs well on fuel that's commonly available.

 

had the exact same issue.
all 4 master caution lights illuminated, yet the car ran fine.
my car had 83K.
took my 2018 Fit Sport to the dealer.
they replaced all4 injectors and cleaned the intake system.
it cost $2400.
I am in the process of writing a letter to Honda USA about this issue for reimbursement.
I also am sending them the 4 faulty injectors.
it appears that these fuel injectors are defective from the manufacture.
i will keep the Forum advised of what I hear back from Honda.


.

 

Same issue here - was traced back to a misfire on one cylinder, after some minor pushback the dealer did a cleaning of the engine as the issue in my case was traced back to carbon buildup. Issue has been resolved ever since (Fall 2021)

In other positive news - Honda Canada issued a warranty extension in August 2023 "Warranty Extension: Engine Misfire due to Carbon Buildup on the Intake Valves"

Glad the dealer and Honda did right by me on this.