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Discussion Starter #1 (Edited)
Hey Guys,

I've been trying to track down this issue and have I've no luck discovering what it is. I can't even get my tuning shop to give me a call back and work toward a resolution either, so I'm hopeful someone has some insight.

I just got my 2017 STI tuned, and there were no issues with it on the dyno. Tune came out great, except for when I got it home the next morning and realized that it has a cold start stumble every morning now. It only happens when it's cold for some reason. The car starts up perfect, idle is great, then literally after 20-22 seconds, the car bogs down and it nearly dies. This goes on for about 3-5 seconds, then the car corrects itself, and it goes back to idling perfectly fine. Hot idle is perfect. Drivability is great. Car made great power. No other issues or CELs with the vehicle. No idea what's causing this.

I have seen a few other random references to this same issue on 2016-2018 model STIs for some reason. I don't know if this is a change in the ECU or how they are tuned? Anyone have any ideas? I'm suspecting this has something to do with the TGV delete, but, those have been being removed on these engines for how many years now without issue. I have also verified the functionality of the stock baro sensor - it is still plugged in and working.


Car has only 10k miles on it, and runs only 93 fuel, compression test came out great when I checked it. Mod list as follows: IAG air pump delete, IAG tgv delete, Cobb intake + box, Cobb turbo inlet, Cobb upppe, Cobb downpipe + full catback exhaust, Perrin EHL, Cobb EBCS, Cobb 20g turbo, Cobb fuel rails, Cobb fuel injectors (1050), Cobb FPR kit, Cobb parallel fuel line kit, AEM fuel pump, Cobb AOS, and Cobb FMIC. I think that's about it.



Assuming I can even manage to get ahold of them, can I somehow get my tuner to unlock my map so I can maybe find anther tuner to look at it? This is my first Subaru since my old 2004 WRX (which was open source). A lot has changed since my last experience.

Thanks in advance. Appreciate it.
 

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This does sound like a tunning issue in my opinion. The car operates great besides a brief cold start idle stumble. Your tuner should be able to correct this and possibly could even correct this without you having to come back in. I believe someone else on here was experiencing the same thing recently and it was just a simple table/parameter adjustment in the tune if i remember correctly.

Now here is my gripe with this whole thing. You just spent the money to get the car protuned somewhere and they wont even give you the courtesy of returning your phone call?? That doesnt sound right to me. How much time has elapsed since you have tried contacting them? I would try giving it a day or so and chaulk it up to them being very busy. If you still can not get a hold of them, then i would suggest you take your business elsewhere and find a new and reputable tuner.
 

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Discussion Starter #3
Well, that's good news that it's likely a tuning issue. That's what I'm hoping. Interested to know what table/parameter was adjusted to get this fixed. I found another shop who's willing to 'fix the issue' but, it sounds like I have to start the tune 100% back from scratch, and it would be a remote tune, so, that's like lighting a match to the money and time I just spent on this tune to begin with.


Yeah, I'm not real impressed with how they are handling it either. It's been over 1 month since the tune. I've sent 3 emails, left 1 voice mail, and talked to an actual guy who was going to 'talk to the tuner and get back to me'. Still...nothing. I actually drove to another state to go see these guys as they were supposedly some of the best around. Happy with everything else, just wish they'd give their customers 5 minutes of their time and at least make an effort to get in touch. I'm going to have to call them back tomorrow and just keep trying until I get ahold of someone I guess.
 

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I always have that stumble whenever I reset the ECU, but only on 2nd start up after the ECU reset.

I saw on my datalog and i think is to do with short term fuel trim learning, as if i recall it will go very lean for a few seconds and then it settles. The subsequent start up won't have this stumble.

But I remembered during the tuning (e-tune), that stumble will always be there whenever i start the car (cold start especially) and i mentioned to my tuner about it and adjustment was made to correct it.
 

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Discussion Starter #7
After about 30+ days of waiting for a revision from my tuner, I finally received one yesterday. The problem is better, but still not resolved. It still stumbles and wants to die, but it's not nearly as harsh as it was. I'm hoping they can resolve this completely here soon.

It was explained to me by them, that for some reason the O2 sensor isn't fully warmed up yet, and the car expects it to be, and then tries to compensate for an overly rich condition, which isn't there.

He said he "adjusted the closed loop delay a bit for this revision to give the front o2 more time to warm up and to allow the post start enrichment table to run a bit longer before entering closed loop mode.".

I'll try to keep this thread updated in the event we get the issue resolved to help others who may encounter this problem moving forward.
 

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Discussion Starter #8 (Edited)
Does anyone know if the maps on an AP are locked? I know the AP itself is married, but what I'm not sure about is the maps.

By that I mean, can I find a different tuner to edit the map my current tuner made and adjust them and see if they can help resolve this issue? Emailed my tuner another log and more information last week, and still haven't heard anything back at all. After dealing with this issue for like 40+ days now since the tune, I think it's safe to say they're not really interested in helping.

** edit - finally got ahold of my tuner, and they want to see the car back. Supposedly, they're scheduling something up next week. Hopefully they follow through, and we can put this issue to bed.
 

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that happened to me after my first tune....took 4 attempts. No tune is perfect out the door. Will have its minor flaws and needs to be driven to find the minor kinks. Though some has came out flawlessly..
 

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I had to same issue, it was a result of tuning. Your tune needs some refinement. Injectors do need a little bit more effort to tune properly. I had to go back to my tuner a couple times to iron out the issues. Finding a knowledgeable tuner, who is helpful and responds to issues is tough.
 

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Discussion Starter #12
Well, I went back to the place who did the tune, they had the car for a week. They were not able to fix it. Supposedly they were going to reach directly out to Cobb to see if they have any ideas, but given how difficult it was just getting ahold of them to look at it again, I doubt I'll hear back.

At this point, I'm still left hanging with the issue. I had another guy who swore it was tune related, and he was going to try to create a map for me to try, but I haven't heard back from him either.

Kinda left wondering if there's an issue with the car, a part, or if it's truly just....tune related? I dunknow....
 

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I gave the same exact problem after having my injectors and car tuned for flex. It'll shoot up to 2k and drop to 1k and then level out. It doesn't happen all the time but occasionally.
 

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Well, I went back to the place who did the tune, they had the car for a week. They were not able to fix it. Supposedly they were going to reach directly out to Cobb to see if they have any ideas, but given how difficult it was just getting ahold of them to look at it again, I doubt I'll hear back.

At this point, I'm still left hanging with the issue. I had another guy who swore it was tune related, and he was going to try to create a map for me to try, but I haven't heard back from him either.

Kinda left wondering if there's an issue with the car, a part, or if it's truly just....tune related? I dunknow....
Do you have a copy of ATR for your AP and car? If so, I can make a map for you today and see if it changes. Additionally, you'll need to do a full boost leak test. You're mods aren't wild, by any means.

I'm still waiting on Cobb to see if they'll grant me with "ProTuner" status, but if you have your copy of ATR, I can do this.

I gave the same exact problem after having my injectors and car tuned for flex. It'll shoot up to 2k and drop to 1k and then level out. It doesn't happen all the time but occasionally.
That isn't necessarily a problem, as you explain it. Video would help.
 

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Discussion Starter #16
Do you have a copy of ATR for your AP and car? If so, I can make a map for you today and see if it changes. Additionally, you'll need to do a full boost leak test. You're mods aren't wild, by any means.

I'm still waiting on Cobb to see if they'll grant me with "ProTuner" status, but if you have your copy of ATR, I can do this.
I've done 2 boost leak tests so far, with no discernible leaks as far as I can tell. However, I will say, that I've done each by going into the FMIC pipe coming off of the intercooler. I have the Cobb intake/box, and can't seem to find a proper coupler to boost leak test from the turbo inlet back.


I don't believe I ever had a copy of ATR? I have AT for loading maps from my computer, but that's about it - unless I have access to something I'm unaware of?
 

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I've done 2 boost leak tests so far, with no discernible leaks as far as I can tell. However, I will say, that I've done each by going into the FMIC pipe coming off of the intercooler. I have the Cobb intake/box, and can't seem to find a proper coupler to boost leak test from the turbo inlet back.





I don't believe I ever had a copy of ATR? I have AT for loading maps from my computer, but that's about it - unless I have access to something I'm unaware of?


I got my coupler from Turbo Boost Leak Testers, comes with a valve and gauge right on it. Expensive but I find it to be worth every penny, you can always make your own. There are a few threads on here that show you what parts to get to make one.

ATR isn’t available anymore ever since COBB changed their policy requiring anyone requesting a copy of ATR to take their course before they can get one. Before, you used to be able to request one online, and they made a copy for your AP/car. Anyone who kept their copy, can re-use it with their tuners. If you didn’t get one before the new policy, your SOL to forever use COBB certified pro/e-tuners or pay/take the course yourself to get your own copy.
 

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Discussion Starter #20
I got my coupler from Turbo Boost Leak Testers, comes with a valve and gauge right on it. Expensive but I find it to be worth every penny, you can always make your own. There are a few threads on here that show you what parts to get to make one.

ATR isn’t available anymore ever since COBB changed their policy requiring anyone requesting a copy of ATR to take their course before they can get one. Before, you used to be able to request one online, and they made a copy for your AP/car. Anyone who kept their copy, can re-use it with their tuners. If you didn’t get one before the new policy, your SOL to forever use COBB certified pro/e-tuners or pay/take the course yourself to get your own copy.

Yeah, that's what it looked like to me, it looks like it wasn't available unless you took some course from them, which sucks. I think I'm kinda SOL on that route.

At this point, I'm pretty confident there's no boost leaks. The only place left to check is where the inlet attaches at the turbo. I've tested from the turbo onward with no signs of any leaks.

The problem isn't really attaching something to it, but more so getting it inside the Cobb intake box. It's a huge pita to remove and stick something inside.


I've heard some good things about Boxer4Racing out of NC, and there's another shop near Atlanta that claims they have had success dealing with this. I just need to find a decent shop I think and get the vehicle checked over and returned, and then fight TopSpeed to refund my money for the tune. I read so many positive things about them in the past, but their level of customer service and tuning has clearly went down hill, I'm sad to say.
 
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