New here, need help with Stutter

[Syphrus]

So i bought a 2017 Si. It has since developed a stutter during acceleration. It has CAI, dowpipe(catted PRL) frontpipe, full exhaust, Mishi Intercooler and piping, prl flex fuel kit. I just put new plugs in it today and that didnt help. It had a dyno tune(which i unforunately lost in trying to figure this issue out) and i have since tried the base ethonal tune, as well as factory tune. I also tried with the factory intake(car came with injen CAI) Stutter persists although its less intense under lower boost. ive attached a short data log, but i apologize if it isnt exactly whats needed as im very new to this. Hoping i zipped/attached it correctly. ANY help is appreciated.

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[Syphrus]

Better description, so when it starts making boost in higher throttle, it will stutter, almost sounding like a suppressed uzi, and obviously doesnt accelerate like it should when it does. Almost seems like a misfire. Im not getting any Knock detection when this happens. My Kcontrol is around .56-.60 The first pull in the datalog, it was doing it bad. Only thing i can really see in the data is the AFR seems to be fluxuating. but i cant really see the reason why. Thanks ahead of time!

 

[rhino]

i feel this might be a question for @gtman he is the guy when talking about tuned cars he might know what the issue is maybe

 

[Syphrus]

Thanks man! I'm thinking it's not the tune that's the problem, seeing as it has repeated the problem on the dyno tune and 2 basemaps. I was trying to monitor the drive to work. It drives fine if I keep it under 60% pedal or so. And I noticed that even under that amount of pedal, the tplate is sometimes as high as 90% but it still doesn't seem to have the stutter, only when the throttle is opened more than that. The o2v looks like its bouncing around a lot, and not sure if that's normal for a wideband? Yesterday I checked the accessible ic piping, reinstalled the injen intake(although I do plan on replacing it as it takes ltft from -3 to -7) replaced the plugs(didn't look bad but smelled a little of oil maybe?) Cleaned the maf sensor. The afr seems to be on target until it stutters, then it kinda bounces around. I'm really clueless on what could be.

 

[gtman]

Yeah, the Injen is about the worst name brand intake for our cars. Just curious what you gapped the new plugs to.

Have you considered going with John Vega or Derek Robinson for an e-tune? To me, with full bolt ons and flex fuel, that's the way to go.

 

[vandalSI]

get rid of the injen intake. it seems to be a problem with a lot of members' cars.

 

[Syphrus]

So the original gap of the plugs was under .020(I'm assuming from the shop that dyno tuned it) I regapped original plugs to .028 with same problems. New plugs gapped to .025 same problem. It had ignition project coils packs, I had one go bad on way to work the other day. I replaced with autozone special to get home. Put OE coils back on. Same problem with all. I am certainly replacing the injen once I get this issue straightened out(haven't decided on 27won or PRL) But since the problem persisted with OE intake installed, the intake is lower on my priority list. And I am definitely interested in an E-tune(D-Rob) but want to get this issue straight first. And since it has stuttered the same on all tunes, I don't think an Etune would fix me up. I do plan on taking the bumper off to check all boost connections this weekend. I just assumed since I'm hitting command targets, that's not likely. I'm kinda leaning toward o2 sensor issue, or possible head gasket/rings issue? does anyone's throttle plate show 101% under WOT? Lol.

 

[gtman]

But the thing is, if you go with D-Rob for an e-tune, he will likely be able to give you input on what the issue might be. I'd contact him and explain the situation along with some datalogs.

 

[Syphrus]

Good call, I appreciate ya. I'm going to do a compression test on it when I get home today just to rule out the severe stuff, then will get ahold of him. There is likely something in the logs that I'm overlooking that a pro tuber could catch easy.

 

[Syphrus]

I also noticed that VTS is always off. I know this isn't the typical vtec system, but is that normal?

 

[Syphrus]

So some updates. I got home and did compression checks. Originally forgot to do WOT, got 115/100/115/100. Tried wet got over 200 on all. Rode out to get head gasket detection kit(blue liquid) when I got back, did WOT dry compression and got 175/170/175/170. Did the coolant check while my son revved to redline to try and get some boost and liquid stayed blue(although it's not high boost at sitting still, so still not definative) reason I was paranoid about head gasket is I had to add some when I brought the car home(was some in the reservoir, but I didn't realize adding wouldn't immediately change the level) and I read a quote from DRob that one symptom of head gasket is slight misfire on cold start. This car does this on morning startup for about a second then clears up. BUT as I was looking around the engine bay, I realized the flex fuel connector(to the box) was barely connected. It wasn't clipped on, just kinda chilling there. I connected it and took some test drives, problem seemed immensely better. Still stuttered a few times, but seemed to get better the more I drove. I guess tomorrow will tell if the computer is just re-calibrating, or if it running better was just coincidence. Fingers crossed it was something that stupid.

 

[Syphrus]

Also, side note, while doing some harder driving, my LTFT with the POS injen CAI was almost -9. So long as the stutter goes away, I will be replacing that within the week. I feel bad trying to sell the injen. :/

 

[gtman]

Also, side note, while doing some harder driving, my LTFT with the POS injen CAI was almost -9. So long as the stutter goes away, I will be replacing that within the week. I feel bad trying to sell the injen. :/

Donate it (to someone you don't like). lol

Or you could donate it to your nearest trash can.

 

[Syphrus]

? sounds about right. Maybe I can find a use for it around the house. Make a better lamp than intake.

 

[Syphrus]

Back to stuttering on the way in this morning. Boost leak check this weekend.

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