Engine stutter on cold start?

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KOIVUN1

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Cool sounds like a good plan. Theres some coolant in your oil though. I did oil analysis even after replacement and there was coolant in there a while. What hardness steal does MAP use? I didnt trust it. Better be tungsten carbide for $150. At least ARP washers specify 8740 Chrome Moly heat treated.

IMG_20211026_120603.jpg
ah i meant no signs of coolant, so i'm just gonna wait until the HG job for new oil just bc i wasn't planning on it so money is a little tighter than usual, otherwise i would. but since the HG job includes new coolant and new oil, might as well just let them do the swap.

idk ab what kind of steel they use but on their website they say "8740 chromoly steel 12pt nuts" so not really sure if that also includes the spacers but i doubt they have a justified reason for charging $15 a spacer.

i keep getting confused on what the machine shop does and what it's worth. the shop i'm having do my clutch (URW for reference) says per manual it's a 17.1 hour HG job, and then plus fluids gaskets and machining charge, worst case price i'm looking at $2750.
the other shop which is more or less just a general repair shop (SJM for reference) (i trust this shop, been going there for 5+ years) tells me 14hrs for labor and then maybe $1000 for their machine shop to do their thing, totaling maybe $3000, maybe more.

the part i'm so confused by is URW tells me the machining would be $500 total, worst case. he tells me they put the head on a vacuum plate to check for cracks as well as valve seating, then it's like $250 to deck it ~.001.
SJM however tells me they put the head in some crazy machine to check every part to see if it's to spec, and they do some magnetic particle/xray/uv light/sciencey bs, and that is also the reason they would charge ~$1000 for the head machining job.
now, SJM is a shop that your grandma would take her car to for overheating. URW is a shop that your grandpa would take his MKV Supra to for a manual swap.
it's just so hard to choose which shop to go to when one tells you they will cover all bases and the other says i'm getting ripped off for $1000 machining job.
any input?
 

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I would estimate 1500 labor, 700 parts, 300 deck the head puts you out about $2500.

That $1k machine job is as big a rip as those spacers. You can get a CNC, ported, polished head from 4p for like $1250
 
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I would estimate 1500 labor, 700 parts, 300 deck the head puts you out about $2500.

That $1k machine job is as big a rip as those spacers. You can get a CNC, ported, polished head from 4p for like $1250
yeah per manual the HG job is 17.1 hours, and URW told me they'd charge for the time so if they do it faster than 17.1 hrs they wont charge me for 17.1.
add in gaskets and fluids/filters, he said no more than 500 total for the machining, worst case price 2750, so most likely less than that, considering it's a new car and less likely for bolts to break/be rusted out.
ordered stud yesterday, gasket from tsp comes next friday. i'm scared to drive the car tbh, idk reading about that other guy blowing his motor has got me worrying more.
 
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So my Cometic head gasket from TSP arrived today, and upon inspection of the label, it says L15B7 16-19 73.5mm
is the 2020 Si not 73.5mm? purely out of curiosity, i doubt it's anything terribly important.
 

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So my Cometic head gasket from TSP arrived today, and upon inspection of the label, it says L15B7 16-19 73.5mm
is the 2020 Si not 73.5mm? purely out of curiosity, i doubt it's anything terribly important.
All L15B motors have 73.5mm bore. Is it .024 thickness?
 


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All L15B motors have 73.5mm bore. Is it .024 thickness?
yessir
idk i just raised an eyebrow that it said 16-19 not -20
also, maperformance’s arp kit came in today, and the spacers have a chamfer on the od on one side, any clue as to whether that faces the block or to the nut?
 

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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!
this used to happen to mine as well. i found that the issue was the clutch and flywheel. On cold starts the flywheel is still cold, so it hasnt expanded yet so it has trouble catching. once i replaced my clutch and flywheel the problem went away. you can test it if you want. drive the car around for a few minutes and turn it off and on again and see if it makes a difference. if it starts up without hesitation then it might be time for a new clutch and flywheel. Don't reuse the old flywheel!!!!!. Some shops would recommend that you resurface it, but the same problem is going to happen. I cheaped out the first time and resurfaced, but now im having to replace the clutch and flywheel this time again. the flywheels warp really easily and once they do, they will tear up your clutch and make the same problem occur.
 
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this used to happen to mine as well.

On cold starts the flywheel is still cold, so it hasnt expanded yet so it has trouble catching.
lmao thanks man but i already figured out the issue and it had absolutely nothing to do with the clutch
maybe you're confusing the engine stuttering with the trans stuttering? like not bogging the engine the engine was legit misfiring because i lifted my head and blew the head gasket which let coolant in the cylinders. on cold start (and eventually warm start) it would sound like a subaru, i think i linked a few videos in the first couple pages.

definitely unrelated to the clutch

i am however replacing my clutch simply because my driving style got me in a new set of tires - more specifically a set of michelin PS4S's - and since those don't spin, my clutch did instead.

On cold starts the flywheel is still cold, so it hasnt expanded yet so it has trouble catching.
also i dont think the flywheel expands much my guy. sure, the friction disk has to warm up to have complete grip but if your flywheel is expanding i think you've got bigger problems on your hands
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