Engine stutter on cold start?

[KOIVUN1]

TLDR: car stutters on cold start, need help with diagnosis

What's up everyone, I seem to be having a new issue that i can't find any related discussion to. Recently my Si has started to intermittently stutter on a cold start. It stutters very briefly, for only a few seconds or so, and then continues to idle normally. Here is a video i took as documentation. If needed, i can note the temperature outside, the humidity, the fuel level, anything that's needed i can take note of.

I've had the Phearable 1.5 tune flashed to my car for roughly 6 months no issues besides clutch slip. I tuned with KTuner V2 and flashed a total of 3 or 4 times since i initially didn't have my cai or fmic+cp installed, so i used the starter maps for a week or so but other than that no other tuning changes have been made.

Only in the past 3-4 weeks has it begun to stutter like this, it's not something that's been around for a while. As the days go on i'm able to listen to different parts of the car after starting it, and the last thing i noticed was the sound coming from the engine bay being way off from what it usually is. Maybe a failing injector or spark plug/coil pack? The strange thing is that the stutter goes just as fast as it comes, and if something was failing wouldn't the stutter remain?

Any help is really appreciated, thanks in advance!

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[KOIVUN1]

Welp. P0300, P0301, P0302.
From what i can gather i’m assuming the rough idle is from misfiring or maybe ‘mid’-firing. injectors seem to be the usual culprit
i haven’t swapped coils or plugs yet, i think i’ll call honda tomorrow and see what’s up.
i’ll flash to stock tune tonight, and i’ll upload a datalog i got of the rough idle, should anyone want to see what happened.
i’ll also upload and link a video i took showcasing the sound of the idle.
fml

 

[KOIVUN1]

video clip of today’s misfire event:
i’ll edit this in a few hours once i’m home to add the datalog.

here is a google drive link to the datalog, not sure how else to upload it also with the proper zip file below

 

[bbeem]

Pull the plugs and swab the piston head with a Q tip. Is it wet? What do plugs look like?

 

[gtman]

What's really surprising here is he's running a fairly conservative tune with minimal bolt ons and he has a low mileage car. I think less that 15,000 miles total.

Seems to me maybe this is a dealer visit because I'd be surprised if the tune caused this. I wonder if it's some sort of defective factory sensor or something.

The usual culprlts ... coils, injectors, plugs... are hard to imagine with so few miles on the clock. Anything's possible though especially with our crap injectors.

 

[KOIVUN1]

What's really surprising here is he's running a fairly conservative tune with minimal bolt ons and he has a low mileage car. I think less that 15,000 miles total.

Seems to me maybe this is a dealer visit because I'd be surprised if the tune caused this. I wonder if it's some sort of defective factory sensor or something.

The usual culprlts ... coils, injectors, plugs... are hard to imagine with so few miles on the clock. Anything's possible though especially with our crap injectors.

phearable 1.5, cai fmic cp exhaust, just hit 16k, around 11k tuned (i think).
definitely gonna flash to stock, call the dealer, set something up...
i leave for hawaii for 9 days on tuesday tho, not sure what to do about that. do i deal with them calling me while im enjoying vacation or wait until after, no clue.
my gut goes to the injectors, as every other thread i've seen mentioning a rough idle ended up with replacing the injectors, especially one mentioning rough idle ONLY on a cold start.

 

[KOIVUN1]

how else can i upload a kdlg file? civicx says it's not allowed

 

[KOIVUN1]

got it, zip file here as well

 

[KOIVUN1]

after flashing to stock and driving a decent amount to reset the meters should the dealership check them, i ended up with a p0301 code yesterday. i preemptively started a log assuming this would happen, and the log shows 205 misfires on cylinder 1 in roughly 15 seconds of rough idle. i didnt check the misfire count on the other cylinders from my other log, but i'm sure they're up there as well. it's very curious as to why i got p0301 AND p0302 codes the first time, but only p0301 this time. i will say though, when the 2 cylinders were misfiring, the idle was SUPER rough, shaking the whole car. i guess all i've been experiencing with the rough idle have been tiny misfires, mostly from lack of fuel vs little/no fuel.
ugh. off to the stealership today.

 

[CAPTS]

the codes gotta be cleared with a proper obd tool even if it's not showing on KTuner.
chk plug gaps & coil packs, could be injectors but not forgetting fuel pump too, a pic of piston top would be good too.

hope you can get it fixed & appreciate if you can share the solution/problem causing it later.

 

[KOIVUN1]

the codes gotta be cleared with a proper obd tool even if it's not showing on KTuner.
chk plug gaps & coil packs, could be injectors but not forgetting fuel pump too, a pic of piston top would be good too.

hope you can get it fixed & appreciate if you can share the solution/problem causing it later.

i’m only clearing the codes so i can drive with my nannies, as they all disable if the check engine codes are on the dash. i’m also not sure how limp mode works, and if the codes aren’t cleared idk maybe it won’t be happy with how i drive. if anything i’d want the codes to be somewhat accessible so when i take it to the dealer they can see that the codes were there.
i can’t do any of that on my own atm; plugs packs or pistons - i’ve been running around for my sisters wedding which is in a week and i fly out on tuesday for two weeks so this project will be on hold for a short while
hopefully i get to the bottom of it

 

[KOIVUN1]

welp it seems my luck with the dealer is running low. i dropped my car off on saturday for them to diagnose the misfires. the guy ended up telling me that they had to replicate the problem in order to work on it. makes sense, but this isn't a squealing brake or grinding wheel bearing that you can induce and repeat consistently. this is my injectors (at least what i think) failing intermittently and not consistently. they've done around 10 cold starts so far and no misfires or rough idles.

im gonna pick it up tomorrow and discuss some ideas with the tech there.
why does it have to misfire in their hands for them to be allowed to work on it? that's utter bs. the rough idle goes away within 15 seconds anyways so what could they possibly do in that short span of time? he says they want to gather data and numbers from the car when it does the thing.

i'm wondering if i should tell him that i have a couple datalogs of it happening. my dilemma comes from the fact that they're ktuner datalogs and i'm not sure if it's a good idea to give them the info that i have a ktuner. he did ask if it was tuned and i told him no, because i've ruled out the tune as the issue since it happens on stock tune as well as my phearable 1.5 flash.

from what i've discussed with the guy, the next course of action for me is to sit and wait for it to misfire again, to the point where it throws the codes, and then bring it to them with the cel still on and codes not cleared. again, not sure what this will do for them other than have them see directly that the cel is on and the codes are thrown. not that big of a difference from right now since i sent them the pictures of the cel on and the codes as well as videos of the misfiring cold starts. tbh it's getting my nerves at this point and i want to diy but idek how DI injectors work and i shouldn't even have to thats the worst part! i bought the car brand new in January this year, there's absolutely no reason i should have to do any of these repairs on my own!

ok rant over. i'll talk to the guy tomorrow, see if i can do anything next time to make sure this issue is taken care of. maybe i'll show him some posts from guys like @DRUSA saying there were a few bad batches of injectors or the quote from @gtman 's convo with drob about the most common causes of misfires. also hoping my clutch from @Unity Performance ships soon! not sure my clutch will hold up for much longer.

if you've read this far you're a real g, leave a like so i at least know i'm not the only one who sees what madness this is. peace out

 

[TripleDeckerPBJ]

welp it seems my luck with the dealer is running low. i dropped my car off on saturday for them to diagnose the misfires. the guy ended up telling me that they had to replicate the problem in order to work on it. makes sense, but this isn't a squealing brake or grinding wheel bearing that you can induce and repeat consistently. this is my injectors (at least what i think) failing intermittently and not consistently. they've done around 10 cold starts so far and no misfires or rough idles.

im gonna pick it up tomorrow and discuss some ideas with the tech there.
why does it have to misfire in their hands for them to be allowed to work on it? that's utter bs. the rough idle goes away within 15 seconds anyways so what could they possibly do in that short span of time? he says they want to gather data and numbers from the car when it does the thing.

i'm wondering if i should tell him that i have a couple datalogs of it happening. my dilemma comes from the fact that they're ktuner datalogs and i'm not sure if it's a good idea to give them the info that i have a ktuner. he did ask if it was tuned and i told him no, because i've ruled out the tune as the issue since it happens on stock tune as well as my phearable 1.5 flash.

from what i've discussed with the guy, the next course of action for me is to sit and wait for it to misfire again, to the point where it throws the codes, and then bring it to them with the cel still on and codes not cleared. again, not sure what this will do for them other than have them see directly that the cel is on and the codes are thrown. not that big of a difference from right now since i sent them the pictures of the cel on and the codes as well as videos of the misfiring cold starts. tbh it's getting my nerves at this point and i want to diy but idek how DI injectors work and i shouldn't even have to thats the worst part! i bought the car brand new in January this year, there's absolutely no reason i should have to do any of these repairs on my own!

ok rant over. i'll talk to the guy tomorrow, see if i can do anything next time to make sure this issue is taken care of. maybe i'll show him some posts from guys like @DRUSA saying there were a few bad batches of injectors or the quote from @gtman 's convo with drob about the most common causes of misfires. also hoping my clutch from @Unity Performance ships soon! not sure my clutch will hold up for much longer.

if you've read this far you're a real g, leave a like so i at least know i'm not the only one who sees what madness this is. peace out

This is all so interesting, man. I have yet to see and hear the videos you posted (at work), but when I am able I'll like to watch and hear them. I had this weird issue where I would get a rough start, as well as trouble getting (back) down to idle for my car, particularly after I've washed my car (while the engine is warm, typically), or when I've driven in heavy rain on the highway. I've suspected the humidity doing something wonky with my MAF or something, because this only happened when water (as above) is in the equation.

If I were idling my car on a cold start, like after a wash, it would kind of idle alright if it was still warming up. But if I give the throttle a little tap (prob about a 300-400ish rpm increase) from wherever the engine is idling (so, either warmed up or still warming up), and let the engine go back to idle from that throttle tap, the engine would reach where it was initially idling at, then almost die and catch itself, going down in rpm while doing so. This drop in rpm, and the subsequent 'catch' the engine has to do, spans just a couple of seconds, then the engine will continue to idle at where it was before that tap on the throttle. Driving a bit and getting the engine fully warm typically helped; though one time it was not fully 'fixed' from the drive I did, since the idle was roughly around 790rpm or so, instead of 700ish. Iirc, the engine was running pretty lean during these weird rough idles, but I can't recall.

I had the Injen CAI at the time, and swapped to the PRL one since then. I haven't had these issues since the swap, even when driving in rain. It was, and still is, very interesting and pretty confusing as to what is even happening. That's why I would love to see your videos and see if your issue is remotely similar to what I've had. Because I'm still paranoid in the back of my mind about this issue I've had, and any potential harm it could cause. I didn't have any codes or CEL, however.

Anyways, hope you have a great vacation, and that other people can chime in if they've had anything similar either. I *think* I made a post about my issue awhile ago through here, if you're curious, but I honestly don't remember lmao. Good luck!

 

[Unity Performance]

welp it seems my luck with the dealer is running low. i dropped my car off on saturday for them to diagnose the misfires. the guy ended up telling me that they had to replicate the problem in order to work on it. makes sense, but this isn't a squealing brake or grinding wheel bearing that you can induce and repeat consistently. this is my injectors (at least what i think) failing intermittently and not consistently. they've done around 10 cold starts so far and no misfires or rough idles.

im gonna pick it up tomorrow and discuss some ideas with the tech there.
why does it have to misfire in their hands for them to be allowed to work on it? that's utter bs. the rough idle goes away within 15 seconds anyways so what could they possibly do in that short span of time? he says they want to gather data and numbers from the car when it does the thing.

i'm wondering if i should tell him that i have a couple datalogs of it happening. my dilemma comes from the fact that they're ktuner datalogs and i'm not sure if it's a good idea to give them the info that i have a ktuner. he did ask if it was tuned and i told him no, because i've ruled out the tune as the issue since it happens on stock tune as well as my phearable 1.5 flash.

from what i've discussed with the guy, the next course of action for me is to sit and wait for it to misfire again, to the point where it throws the codes, and then bring it to them with the cel still on and codes not cleared. again, not sure what this will do for them other than have them see directly that the cel is on and the codes are thrown. not that big of a difference from right now since i sent them the pictures of the cel on and the codes as well as videos of the misfiring cold starts. tbh it's getting my nerves at this point and i want to diy but idek how DI injectors work and i shouldn't even have to thats the worst part! i bought the car brand new in January this year, there's absolutely no reason i should have to do any of these repairs on my own!

ok rant over. i'll talk to the guy tomorrow, see if i can do anything next time to make sure this issue is taken care of. maybe i'll show him some posts from guys like @DRUSA saying there were a few bad batches of injectors or the quote from @gtman 's convo with drob about the most common causes of misfires. also hoping my clutch from @Unity Performance ships soon! not sure my clutch will hold up for much longer.

if you've read this far you're a real g, leave a like so i at least know i'm not the only one who sees what madness this is. peace out

Darn, it's frustrating indeed chasing rogue issues. Hope it gets sorted soon!

New stock of Competition Clutch arrived this evening, yours will be sent out tomorrow

 

[KOIVUN1]

Darn, it's frustrating indeed chasing rogue issues. Hope it gets sorted soon!

New stock of Competition Clutch arrived this evening, yours will be sent out tomorrow

hell yeah i'm stoked!! not so stoked about the $1300 quote for the install ugh my wallet is gonna hate me. next up after the clutch (and this issue) is a downpipe and exhaust and then brakes
unity-performance.com FTW!!!

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