20 second stumble on cold start 2018 STi

[Zcypot]

Originally Posted by STIAH64

Now I am yes, even when I was Hybrid I had the same exact issue. I’m not even on E, Pump 93 until I figure this issue out.

yeah I think im hybrid as well, because my tuner said it was still using the MAF but its SD.

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[Haive_Music]

Originally Posted by STIAH64

I’m having the same issue from now 2 reputable tuners. Video link:
http://youtu.be/im_pzbEjw_Q

Yup, this is *exactly* what mine does too. Mine has done this with my first tune, and I thought it was tune related, but I was just retuned yesterday at another tuner, and the car does the same thing.

I will be reaching back out to the new tuner tomorrow to see if he has any thoughts on clearing it up. I'm on MAF, for what it's worth.

[STIdreamn]

Originally Posted by STIAH64

I’m having the same issue from now 2 reputable tuners. Video link:
http://youtu.be/im_pzbEjw_Q

2018 STI

Block:
-OEM Block
-Closed Deck
-Pinned Mains
-Manley H Tuff Rods
-99.75 bore 8.5:1 Manley XD pistons
-King Subaru Bearings (main and rod)
-Killer B oil pickup and baffle
-Fluidampr Damper
-ECM Billet timing guide
-ARP Head Stud kit

Turbo:
-FP Black HTZ

Intercooler:
-PRL FMIC

Exhaust/Manifold:
-Killer B 4-1 EL headers wrapped
-Killer B Uppipe (vbanded)
-44 Tial EWG 17lb spring
-Dump tube
-Invidia (divorce plate) Catless DP
-R400 catback*

Intake:
-Cobb with box
-84mm turbo inlet
-Turbosmart BOV (in BPV config)

Fuel:
-DW 300c Pump
-Fuellab universal EFI regulator
-IAG Fuel Rails
-IAG Fuel line kit
-ID 1000 injectors (top feed)
-IAG TGV deletes

Sensors:
-Grimspeed 3 port boost controller
-Innovate Wideband
-Cobb fuel pressure sensor
-Cobb 4 Bar MAP Sensor
-Viscounti w/ IAT Hybrid MAF harness
-Electric oil temp and pressure

Other:
-IAG AOS competition
-Mishimoto Oil Cooler
-Air pump delete plates
-ACT XT-M perf Street Pringle clutch

My friends 18 doesnt even have a built motor yet and still to this day we haven't gotten an answer. For now he is living with it as two of the best tuners in our area aka wkd matt and brentuning haven't figured it out. The guys at bren essentially would have to take everything out check then reinstall as the didn't do the physical work and already fixed a couple major issues before retuning.

Have you guys watched the signal from the front 02 at all when this happens? Once it warms up and goes to change cycles it seems to stumble until finding itself again. Happens too fast to get a good log and understanding of why.

[rtv900]

Originally Posted by STIAH64

I’m having the same issue from now 2 reputable tuners. Video link:


2018 STI

Block:
-OEM Block
-Closed Deck
-Pinned Mains
-Manley H Tuff Rods
-99.75 bore 8.5:1 Manley XD pistons
-King Subaru Bearings (main and rod)
-Killer B oil pickup and baffle
-Fluidampr Damper
-ECM Billet timing guide
-ARP Head Stud kit

Turbo:
-FP Black HTZ

Intercooler:
-PRL FMIC

Exhaust/Manifold:
-Killer B 4-1 EL headers wrapped
-Killer B Uppipe (vbanded)
-44 Tial EWG 17lb spring
-Dump tube
-Invidia (divorce plate) Catless DP
-R400 catback*

Intake:
-Cobb with box
-84mm turbo inlet
-Turbosmart BOV (in BPV config)

Fuel:
-DW 300c Pump
-Fuellab universal EFI regulator
-IAG Fuel Rails
-IAG Fuel line kit
-ID 1000 injectors (top feed)
-IAG TGV deletes

Sensors:
-Grimspeed 3 port boost controller
-Innovate Wideband
-Cobb fuel pressure sensor
-Cobb 4 Bar MAP Sensor
-Viscounti w/ IAT Hybrid MAF harness
-Electric oil temp and pressure

Other:
-IAG AOS competition
-Mishimoto Oil Cooler
-Air pump delete plates
-ACT XT-M perf Street Pringle clutch

Was that massive mod list worth it considering the pitfalls?

[STIAH64]

Originally Posted by rtv900

Was that massive mod list worth it considering the pitfalls?

For me it’s worth it because I truly enjoy Subaru’s and this platform. It may not be the most cost effective way to get the power compared to other platforms, but it’s there. Honestly other than this small inconvenient issue, I’ve has no issues on this setup for the last 15k.

[Boxer112]

Barometric pressure sensor. When I did my big build, it was accidentally taken out. Not until I purchased a new one and installed it did this problem go away. No need to retune for it either.

[STIAH64]

Originally Posted by Boxer112

Barometric pressure sensor. When I did my big build, it was accidentally taken out. Not until I purchased a new one and installed it did this problem go away. No need to retune for it either.

Something so easily overlooked, theoretically it makes perfect sense. I just pulled that bad boy off my shelf (drivers side, big connector as compared to the passenger side because it’s where the sensor is). Took me 10 minutes just to find where the harness was tucked away under the manifold lol but I’ve hooked it up and waiting till morning for a full cold start. If this works, I’ll let you guys know and will be cutting the Sensor out of the housing.

[s.ouzou]

Originally Posted by greygonzalez

I have the same issue. It’s when the rear 02 sensor turns on and the fueling trims go nuts. It only takes a few seconds for it to properly adjust.

At the moment there is no fix from what I believe. I worked with a few tuners who told me this.

My car has been tuned to just turn the rear 02 sensor off and it hasn’t had this problem.

[Haive_Music]

Originally Posted by Boxer112

Barometric pressure sensor. When I did my big build, it was accidentally taken out. Not until I purchased a new one and installed it did this problem go away. No need to retune for it either.

I don't believe this is the cause of the issue.


I thought this at first too, especially since I also removed the air pump at the same time. Either that or that it was related to the TGVs, except those have been being deleted for years without consequence now.

My Baro sensor is still connected, and presumably working. I cut mine off of the cap like I saw some people do, and just left the sensor tucked away in the engine bay. When I log the car, I can see the barometric pressure reading change day to day, location to location, so, I'm assuming it's still working correctly.


I'm unsure if my rear O2 is enabled or not. I'm running a cat, and the sensor is there and connected, so I'm assuming the tuner left it on.



Edit: Just double checked mine, and it seems to be working. Is reading 14.23 today, and it showed 14.07 2 days ago in a data log. 14.23 seems to be a bit low compared to the airport's reading of the pressure, but I'm also slightly up on a mountain, so....?

[Haive_Music]

-----

[STIAH64]

Originally Posted by Haive_Music

I don't believe this is the cause of the issue.


I thought this at first too, especially since I also removed the air pump at the same time. Either that or that it was related to the TGVs, except those have been being deleted for years without consequence now.

My Baro sensor is still connected, and presumably working. I cut mine off of the cap like I saw some people do, and just left the sensor tucked away in the engine bay. When I log the car, I can see the barometric pressure reading change day to day, location to location, so, I'm assuming it's still working correctly.


I'm unsure if my rear O2 is enabled or not. I'm running a cat, and the sensor is there and connected, so I'm assuming the tuner left it on.



Edit: Just double checked mine, and it seems to be working. Is reading 14.23 today, and it showed 14.07 2 days ago in a data log. 14.23 seems to be a bit low compared to the airport's reading of the pressure, but I'm also slightly up on a mountain, so....?

I’ve just tested with the Baro on, no difference since the MAP pressures adjustments were pretty damn close already at sea level. Leaving it on to eliminate that possible issue.

I have my rear 02 enabled but only because I have my Wideband tapped into the rear 02 harness to log on the access port. Everything is pre cat and functional / calibrated.

[STIAH64]

Originally Posted by s.ouzou

My car has been tuned to just turn the rear 02 sensor off and it hasn’t had this problem.

Just to clarify you had this issue prior to shutting off the rear 02 sensor. Then when disabled the rear 02, the problem went away? Are you running a Wideband to gauge only with no physical connection to the ECU?

[Haive_Music]

Originally Posted by STIAH64

I’ve just tested with the Baro on, no difference since the MAP pressures adjustments were pretty damn close already at sea level. Leaving it on to eliminate that possible issue.

I have my rear 02 enabled but only because I have my Wideband tapped into the rear 02 harness to log on the access port. Everything is pre cat and functional / calibrated.

It sounds like you've got the ability to adjust your tune yourself there at home. I'd be curious to know if you temporarily disabled your rear O2, if the issue goes away tomorrow morning for you or if it still remains.

I have no way of editing my map unfortunately, and still haven't heard anything back from my tuner yet about this.

[Boxer112]

Originally Posted by STIAH64

I’ve just tested with the Baro on, no difference since the MAP pressures adjustments were pretty damn close already at sea level. Leaving it on to eliminate that possible issue.

I have my rear 02 enabled but only because I have my Wideband tapped into the rear 02 harness to log on the access port. Everything is pre cat and functional / calibrated.

So nothing changed?

Have you reset your ECU?

Sad that didn’t fix.

[STIAH64]

Nothing changed with the idle issue, and yea reset the ECU. This is frustrating. Rear 02 shouldn’t have an effect on the cold start but worth a shot since I’m out of ideas.

[Mokoman1998]

Exactly the same issue here. 2018 STI all the bolt-ons + e85, except turbo. Has died on me once... tuner (brentuning), states that it could possibly be from the e80 fuel, recommended me to put e60 to see if it solves. Nothing yet. Its just a minor inconvenience.

[STIAH64]

Originally Posted by Mokoman1998

Exactly the same issue here. 2018 STI all the bolt-ons + e85, except turbo. Has died on me once... tuner (brentuning), states that it could possibly be from the e80 fuel, recommended me to put e60 to see if it solves. Nothing yet. Its just a minor inconvenience.

I think we can rule fuel out due to the variety on this thread from Pump 93 through E85. There’s no way we could all be experiencing the exact same issue with the variety of different builds. It has to be ECU or tune related. It seems to be ONLY 2018 Sti’s with this problem 🤔 But then again the variety of top tuners we’re using would have caught this. This doesn’t make any sense! Perhaps something changed or is not programmable in the 18 model STI’s vs all other model years ECU’s?

[Mokoman1998]

Very possible. I wouldn't be surprised if its ECU related. I'll email my tuner tomorrow with this information.

[Haive_Music]

Originally Posted by STIAH64

I think we can rule fuel out due to the variety on this thread from Pump 93 through E85. There’s no way we could all be experiencing the exact same issue with the variety of different builds. It has to be ECU or tune related. It seems to be ONLY 2018 Sti’s with this problem �� But then again the variety of top tuners we’re using would have caught this. This doesn’t make any sense! Perhaps something changed or is not programmable in the 18 model STI’s vs all other model years ECU’s?

I'm on a 2017 and am affected by this running 93. It's definitely not only 2018's, or related to E85.


I've had 2 people tell me it's related to the air pump delete now, but still no word on a fix. It just seems odd to me, as people have been removing those for quite some time now. It would make sense that it would be related I suppose, after about 20 seconds the air pump would kick off, and the car would probably cut the amount of fuel it's injecting to compensate for that. Still, you'd think there would be compensation tables for this, and other years would have seen this issue happening before now.

[Mokoman1998]

The thing is I don't have an air pump delete, not sure if a possible leak could be an issue but ill get around looking at it.

[Haive_Music]

Originally Posted by Mokoman1998

The thing is I don't have an air pump delete, not sure if a possible leak could be an issue but ill get around looking at it.

Interesting. Do you have TGV deletes?

[Haive_Music]

Any news on this?

STIAH64 - Did you ever get a chance to disable your rear o2 and see if this resolves the issue?


I can't even get the shop who did my tune to call or email me back. I sent them in a log per their request about the issue, and almost 3 weeks later, I can't get them to pick up the phone or right back.

[STIAH64]

Originally Posted by Haive_Music

Any news on this?

STIAH64 - Did you ever get a chance to disable your rear o2 and see if this resolves the issue?


I can't even get the shop who did my tune to call or email me back. I sent them in a log per their request about the issue, and almost 3 weeks later, I can't get them to pick up the phone or right back. Disappointing given who they are.....

Rear 02 has no bearing on this issue. I think it’s TGV delete related. The fuel trims go crazy right when the TGV would start it’s work. It’s for a specific duration and every cold start, so it would make sense that somewhere the ECU is thinking it’s still there and trying to correct, then over correct and we would have our stumble. The question is why? Every other EJ this can be accounted for, why would it be an issue on ours? This is the question that makes me doubt the TGV and at the same time thinking it is.

[Haive_Music]

Originally Posted by STIAH64

Rear 02 has no bearing on this issue. I think it’s TGV delete related. The fuel trims go crazy right when the TGV would start it’s work. It’s for a specific duration and every cold start, so it would make sense that somewhere the ECU is thinking it’s still there and trying to correct, then over correct and we would have our stumble. The question is why? Every other EJ this can be accounted for, why would it be an issue on ours? This is the question that makes me doubt the TGV and at the same time thinking it is.

You share the same thoughts as I. Just trying to have someone actually test it who is able to eliminate it being a possibility instead of just throwing more blind guesses at what it may or may not be without actually testing anything.

I too feel it's related to TGVs, but again, just like you're thinking, these have been being removed for years now. Why is the issue just now creeping up? More so, I can log my car and see that the TGV setting remains unchanged on start up - meaning, it should be disabled in my tune, so is there something else that's changed or causing the car to think it's still there? I don't know..... Grasping for straws at this point.