chiming in from the 2nd gen forum.
you can test ejectors at home by removing them, then taking one in hand, putting some fuel or fuel cleaner in the top port, and jumping it from the battery. I've used mini butt connectors to that end, some leftover 18g wire. it's admittedly pretty un-fancy, but on older vehicles and those that have sat for periods (unusually low mileage) I've found it useful. if they're gummy, I use fuel cleaner and scrub the emulsifying end (mesh screen or series of small holes) with a toothbrush til i get a proper mist out of them.

with the second gen, its either the loose plug issue or a need for valve adjustment that leads to some crummy running. we've noticed that some specific valves are prone to tightening, though i can't recall which ones.

can't quite pin down a specific fault from this thread.. if we're talking about engaging the clutch at low rpms and clutch shudder, i can give my opinion. the stock clutch seems a little grippy to me I replaced mine at 80k miles with an exedy and put in a new luk flywheel. The replacement clutch has less friction area and is easier to engage.. Though the oem one hadnt worn out, the springs in it did. they absorb a great deal of shock from engagement and can get permanently compressed.
Havin some issues with the site, not lettin me post pictures. i'll try again later.

Another factor in clutch engagement is rolling resistance. an out of alignment vehicle will have more vibration and difficulty engaging, as will one with heavier wheels. kinda screwed myself on that front by picking up sparco terras in 16x7, but the budget was limited. now theres new options out there for a reasonable price.

i'd definitely advocate for adjusting valves, cleaning intake air sensors and around the throttle body plate, and checking spark plugs before replacing some of the fancy electronic components, but i do come from a somewhat different platform. in general i wouldnt go beyond 30k miles between valve adjustments on vehicles with adjustable valves, but for folks who drive a lot i'm sure that could be stretched.

 

my '19 has only 33000 on the odometer , but i just replaced the plugs with NGK IX's . the car definitely feels stronger and that finicky stuttering if i don't hit the clutch just
right seems masked over . it had gotten more touchy in the last two months or so . i'll have to live with it a few days to really know for sure . with my last honda , the iridium plugs
were rated for something like 80-100k . i remember changing them once at 50k and it was quite noticeable . i brought it up with a mechanic , he told me , no , they're not the same
plugs at 80k . so i ended up changing them at 50 .i don't know , it worked for me . i put 240k on that civic .

 

Got video?

Got any codes set (check engine light on)?

How many miles?

If higher mileage, have you ever had the engine's intake valves walnut blasted to remove carbon deposits and/or valves adjusted?

While this is indeed a good idea for multi-port fuel injected first and second gens, I wouldn't encourage it on the third gen with the L15B1.

Reason 1 - The L15B1 has a direct injected fuel system and those injectors are a flow matched set as well as operate at a much higher pressure than the MPI in gens 1 and 2. Without having a flow tester to check how well the injectors were cleaned and how consistent their performance is, OP might be back at square one. Still I will openly admit, cleaning is of course a much cheaper than replacing the full set of injectors AND its fuel joint pipe if one can find a company or someone comfortable with cleaning DI injectors providing supporting and consistent test results.

Reason 2 (the bigger reason) - The fuel joint pipe (runs from the high pressure fuel pump to the fuel rail) is a one time use item as per Honda. It's joints work in a similar fashion to our drain plug crush washers and seals the system when torqued to spec. Under-torquing and/or reusing the existing fuel joint pipe can potentially cause fuel leaks and possible fire.

 

Similar problem, 66k, 2018 Fit---and had PO 420 cat code. So far I changed plugs, even though no record on the scanner of any misfire. Did cylinder AF test, all but cyl 3 ran rich, so I swapped the 1 and 3 coils to see if values changed. After changing plugs, all cylinders ran rich. Read O2 data, all seemed good. Did EGR functional test, all seemed normal. Catalyst temperature and monitors went from ok to not good. I'm inclined to think I have bad injectors, and they're $850 my cost. Then hopefully excess fuel will burn out of the cat and the code doesn't return. Going to talk to my master tech at work tomorrow to get his thoughts and hopefully move forward with the repair. (I dealt with NONE of this with my old 08 Fit)

 

High probability that you're dealing with injector replacement and carbon build up from what you've mentioned. The cylinder AF test saying that one or more injectors are running rich is usually the culprit (but not always) on these direct injected engines.

I'd highly recommend walnut blasting the intake valves as well (which is a service bulletin for 2015 to 2020 MYs) while you're doing injectors. Adjusting valve lash while the car is down would be additional icing on the cake.

 

Thanks Hootie!

 

is there a new version of injectors that doesnt fail? or do we just put new ones in and hope for the best? also anyone know why the injectors are failing? any way to prevent this from happening?

 

As far as I know, there has been only 1 part super-session with the fuel injectors while dabbling on the interweb and various Honda sites.

As for why the fail or get clogged (mind you, this is my own opinion... take it with a grain of salt), is all down to the direct injected fuel system. It does NOT spray fuel on the intake valves to wash off the backside of those valves. Combine that with oil blow by that also gets into the intake and further coats the valves and injectors, the engine would eventually be back at square one with an injector fault. What honestly needs to be done at minimum is periodic walnut blasting as routine maintenance to remove the carbon build up and other varnish in my honest opinion.

BMW, for example, was quick to figure this out with their N54 engine as well MINI (which they also own) with their DI engines in the R56 Coopers around 2008-ish; give or take a year. There are other European manufactures who suggest the procedure routine maintenance as well.

Other manufactures, like Ford on there current wave of EcoBoost V6s, even added auxiliary fuel injectors that would come on during various load situations along with washing those intake valves with fuel while active.

Other aftermarket alternatives would be to add an oil catch can to reduce the amount of oil blow by that goes back into the intake and eventually into the combustion chamber as well. This one is the most common among Honda owners running GDI Earth Dream engines from what I see.

 

so if it's gummed up valves then a walnut blast should be fine and the injectors should be good? Is there a benefit to direct injection over let's say being in the intake manifold like other Hondas? Walnut blast doesn't sound very cheap either.
my coilpacks will be here sometime this week, ill be able to do the plugs and packs this weekend and rule those out. I have 110k on the odometer as it sits now.

 

If anyone's interested, I've got a knock-off of the T-Rev from J's Racing on my GE8. you can add them to anything.. Its just a reed valve with a junky mini air filter that fits into a crankcase vac line. Mounting requires a degree of creativity if you want it to be neat.. I've yet to bother doing a vac test to verify that it maintains negative case pressure, but the line that it's on no longer has any oil in it, nor does my throttle body's "butterfly valve." It substitutes a catch can by negating the pressure that forces oil into a catch can. The questionable part is, for me, the poor quality of the air filter it utilizes. I spent some time looking at air filters for gas-powered rc cars to find a suitable quality replacement 😂 but I didn't follow through.
won't claim any performance perks without data to back it up.

@Hootie I'd like to preface my response by saying that I respect your knowledge on this stuff and think that your method is far more professional and less risky than mine. I've never messed with a direct injection system, and am inclined to believe that you know what you're talking about.

Now, in regards to the fuel rail connections being a one-shot deal, what kinda sealing method do they utilize? I've lubed my share of o-rings and made a few cork/rubber, rubber/cellulose gaskets from sheets sold in packs from amazon for $7. I've also stretched crush washers for multiple uses when necessary, often without leaks, but sometimes they happened. Mostly as a result of a former hand over-tightening the plug and denting the pan. I do acknowledge that this is fuel though, and wouldn't recommend such things, but I'd do 'em myself for sure, and give the injectors a cleaning and a second chance too if they were already write-offs.

 

been driving with new NGK IX plugs for a week now , the stumbling is all but gone . i think i can provoke it if i try ' but for
the most part the car accelerates quite strongly , clutch isn't finicky at all . feels like it did when new . i'm saving the original plugs
to compare them with the IX's . going to change them in 3 years or so , i think the 100k manufacturer's recommendation is way off

 

ive ran about 15oz of lucas through my car which is roughly 5 fill ups and the stuttering is almost gone, only happened 1 time in the last week.
im going to finish the bottle and see what happens. this was the large bottle 30 something ounces i believe. also going to chnage the coilpacks and plugs because i already purchased them.