I have an '18 Fit EX manual, owned since new. On 8/19/23, around 63k miles, I started experiencing the cascading warning lights due to misfire. Initially, the lights came and went and the car ran normally, so I didn't really think much of it. Eventually, all the lights stayed on. I checked the valves, replaced all plugs and then all coils. Never went away. By this time (84k miles) I could feel a slight stutter upon startup and between gears 1/2 (low speed). And the car had gone into limp mode a few times at startup or while driving. Took it in to dealer for fuel pump recall and did walnut blasting and then replaced all injectors. Dealer repair wasn't much more than getting the OEM parts online, so I just had them do it.

Going forward, what is the best way to prevent injector fouling and intake valve buildup? Catch can? Techron every oil change? Impossible? Next time this happens, I'll probably spring for the $80 injectors I saw on Amazon and try swapping them or maybe cleaning my OEM injectors (I kept the originals).I don't drive timidly as I'm used to driving manual Hondas and know you have to get close to redline before the engine really comes to life. I've seen people say use "good" gas, but don't really know what that means. I go to regional/national chain stations so assume the fuel is good.
Is this just a downfall of direct injection that can't be prevented?

 

Run Top Tier fuel exclusively,

These Honda engines are extremely susceptible to carbon buildup. We've seen reports of carbon fouling in engines with as little as 10K miles.

Top Tier gas has detergent additives that are critical for preventing carbon buildup.

One study found 19 times more carbon buildup with non-Top Tier gas:

https://www.consumerreports.org/cars...e-a7682471234/

 

Yes or at best sort of.

Many say you can help by using "top-tier" gas. That's not going to hurt, but a direct-injection engine will inevitably run into issues, especially with carbon buildup on the intake valves, because of direct injection.

This problem is pervasive across manufacturers. Some are going to a sort of dual port- and direct-injection system where (some) fuel is sprayed directly into the intake before the intake valves (as it is on my 2010 Fit Sport), which acts to wash the intake valves clean, with the remainder being injected into the cylinder as it is in your engine. This is probably the "best-of-both-worlds" approach.

 

I’ve had some pretty bad hesitation in first and second gears. I used a full bottle of Redline cleaner and for the first month, it felt equal or even a bit worse. Ever since, I’ve used another half bottle and the hesitation is much, much better. Maybe it’s snake oil but I’ve had good results with injection cleaners, especially redline.

its very easy to use. Wait until the gas tank is nearly empty, then use a whole bottle and fill up the tank. For maintenance, you can do the same with a half bottle.

 

Maybe you have that 1 in a thousand bad engine.

 

With all the injector complaints here and on other various sites on the internet (not to mention official warranty extensions), I highly doubt it.

 

I would say it's due to the absence of port injection. As you said, port injection (and other older / less common flavors like throttle body injection) washes the intake valves with fuel. Without that, oil mist from the PCV system and traces of soot from the EGR system deposit and carbonize on the hot valves.

The modern rebirth of CVCC. Or at least it could be if it weren't emissions-suicide.

 

Buy regular 87 octane gas from reputable gas stations.

Using mid grade or premium gas is a waste of money.

 

I would second that...what ive done so far for 67000KMS...basically brand new

 

I've installed an oil catch can. I'll also probably start regularly using Techron, maybe every oil change. I'll report if I end up having issues in the next 5 years / 85-100k miles. I plan on keeping the car and eventually giving it to my 13 year old.

 

I might have a concern about overdoing the Techron. Always best to follow the recommendations on the label.

 

Good point. I think I read someone else mention that timing on Techron usage. I've never used it, so I'll definitely follow the directions!

 

I used a Mishimoto catch can and did the CRC DI cleaning regularly. No issues. Car unfortunately totalled.

I continue doing that routing in my 9th gen Accord, which also has the DI engine.

 

Chevron has Techron in it already. As I've said before on the forum, a Chevron engineer once told me that you don't need the additional Techron in the bottle. I have used it, but I don't think about it too much anymore.

 

Subarus had the same issues and they've had a cat recall due to it.

You need to run 93 to elongate time between valve changes and keep the motor running efficiently.

Ideally drilling into the intake and adding low pressure fuel injectors would help. Audi has this setup (one injector) on some models. Does wonders.