06 Sti Running Lean with New Turbo Inlet (Smoke Tested) *SOLVED*

[Vanalex]

OEM inlet had a crack, replaced with silicon aftermarket one. Took intake manifold out cleaned out some blocked metal pipes that had gunk, changed out some old rubber hoses that were like plastic. Smoke tested everything 0 Smoke. CAR has CAI, Catless DP. I have an AP I have ran the car at Stage 0, Stage 1 (Ik its for stock), and also on the stock tune unmarried. In this time I have changed the oil to Valvoline restore and protect 5w-30 Engine has 80K miles. Car Ran Fine at some point before, I never redline and stay about 1K away from it aswell. I have Put a brand new Fuel Filter and Pump and it made 0 Difference. DAM is at 0. Shows Knock and FNL under load but since i am running lean when Im even slightly on throttle I dont push the car at all anymore. I have tried putting shell, Chevron, Arco Gas is not the problem. I am from cali and I have even tried the acn91 tunes. I have inspected and cleaned the front O2 it was clean to begin with. I have visually inspected the car from top to bottom on a lift, checked engine harness connections. I also have an AUTEL to reset lights and check on Realtime values.

I am Open to try anything I am pretty mechanically inclined and have searched the forum but it seems that I find people that have a problem within a certain RPM Range where I am having a problem while giving gas regardless.

Questions/Possible leads
Maybe the Oil I put is too light for the older engine (5w-30)?
what line could be pinched to cause this?
Restrictor Pill has been changed from the Stock to a slightly larger one(Boost is still lower than normal due to low DAM)

In the Past I have taken Every Module that has to do with my AC out including the dash because it didnt work (Fixed)
Front Right Speaker Harness was shorted (Fixed)

This is also my First Post But I plan on posting all my Troubleshooting adventures on here

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[Jay11STI]

Smoke test is fine but I would still recommend doing a boost leak test. You'd be surprised what leaks under pressure.

Have you checked your fuel pressure? Ive herd stories of guys making mistakes during fuel pump installs/replacements leading to issues.

Also since you have an AP, what are your AFL1 values?

Since this is an older car, you really should be running the AP stage 2 map at the bare minimum. A protune would be best for your mods.

[Vanalex]

Originally Posted by Jay11STI

Smoke test is fine but I would still recommend doing a boost leak test. You'd be surprised what leaks under pressure.

Have you checked your fuel pressure? Ive herd stories of guys making mistakes during fuel pump installs/replacements leading to issues.

Also since you have an AP, what are your AFL1 values?

Since this is an older car, you really should be running the AP stage 2 map at the bare minimum. A protune would be best for your mods.

Will do the boost leak soon.
Will check afl1 ratios.
How can I check fuel pressure? I am sure I did the fuel pump and filter installation fine because the car didn’t do any better or worse when I changed it out with a walbro 255 and it was very simple.
I don’t have access to the Cobb stage 2 tune, the website only has stage 0 to 2. Would anyone happen to have a link for my cars year stage 2?
I don’t want to get a pro tune at the moment because the car ran fine before I took the whole intake manifold off. I have also checked evap hose routes.

Thank you for the help and moving to the appropriate place.





Just curious if I’m running lean and I fix a boost leak doesn’t that mean I’d be running even more lean ?

[Vanalex]

Today I pulled out the MAF sensor and the car ran fine no Knock or FNL on the AP. Boost was in good range. AFL was at 0 after driving it a little bit but in the beginning it was 14. Dam is at .5 doesn't go up or down presuming that its because of the MAF sensor being unplugged. MY QUESTION now, why is the car running lean (15-16) on WOT but without the MAF sensor its showing 11 AFR on WOT. Car is on stage 0 Tune just to be able to run the AP. If my MAF sensor is the problem why is it that from a 2 day intake installation it went to sheit. Thank you for your help.

[Jay11STI]

Originally Posted by Vanalex

Today I pulled out the MAF sensor and the car ran fine no Knock or FNL on the AP. Boost was in good range. AFL was at 0 after driving it a little bit but in the beginning it was 14. Dam is at .5 doesn't go up or down presuming that its because of the MAF sensor being unplugged. MY QUESTION now, why is the car running lean (15-16) on WOT but without the MAF sensor its showing 11 AFR on WOT. Car is on stage 0 Tune just to be able to run the AP. If my MAF sensor is the problem why is it that from a 2 day intake installation it went to sheit. Thank you for your help.

Sounds like you may have found your problem. Its an electrical component, it can fail at anytime. Its a 2006 so im sure its time. Maybe you looked at this the wrong way during repairs. Id replace it with a brand new oem subaru MAF.

I wouldn't recommend continuing to drive or do WOT pulls without a properly working MAF.

[Unabomber]

You need to REPLACE your front oxygen sensor. Your car is old, so is that sensor and just because it looks fine means zero. Grandma's hip looks fine too, but one fall in the foyer will turn it into powder. OEM or Denso from legit source is what to replace with, not some $18 rockauto jank.

Same with your Boost Control Solenoid. That's OEM only.

Same with your MAF. OEM or Denso from legit source is what to replace with, not some $18 rockauto jank.

The three things can/will fix your issues and/or wake up the car in other ways. Remember....cleaning a MAF or sensor is fine, but they eventually need replaced.

[Vanalex]

LOL keep an eye on grandma make sure she stays away from the foyer till I Get this MAF sensor swapped.

Thanks for the information everyone. I will start by Purchasing a new MAF sensor and if that alone doesn't fix it I will change the front 02 Sensor... YES OEM I made that mistake with my first car (02 BUGEYE by XS engineering).

As far as the boost control solenoid i have tested it off the car at 20psi and no leaks actuates perfectly, haven't done a boost leak test yet but my smoke test built up to .2 psi its a little ancel 3000.

No more WOT, only MOTs (Minimally Open Throttle) pulls .

[Vanalex]

Hello All, My O2 tool has not come in yet so all I was able to do was plug in the new MAF sensor and get some datalogs with it. My Dam didn't go higher than .875 and on WOT I see the AFR is still High. I know this isn't accurate yet since the new O2 hasn't been installed either but I thought I would just give everyone an update if they were interested. I would also like to add that I didn't get to drive it a lot after resetting the ECU so it could've still been relearning plus heavy traffic and cops I couldn't do a higher speed pull. I will be doing a longer drive tomorrow and Monday Installing the new O2.

https://docs.google.com/spreadsheets...it?usp=sharing

[2fvcknfst]

Having a similar issue, but I'm mafless.

[Vanalex]

Changed the maf sensor no difference, changed out the front O2 no difference. All Denso Brand New. When I run the car with the maf sensor unplugged everything runs perfectly again, I am trying to guess where there could be a possible air leak that could be caused from removing the intake manifold and putting it back on. I tried spraying carb cleaner around the intake inlet and hose clamped areas to test for a leak as well as another smoke test but nothing changed or gave out engine was running same. I HAVENT done a boost leak test yet but i am assuming if i had a boost leak it wouldnt effect the cars running lean problem because accounted for air would be wasting instead of accumulating extra, I believe my problem is from the turbo inlet to the intake.

I will try to cover off one turbo inlet hole at a time to try and single out which route the air leak is from because under idle vacuum it is not enough to show up

Any tips would be greatly appreciated thank you.

[Vanalex]

Originally Posted by 2fvcknfst

Having a similar issue, but I'm mafless.

Some Things you can check,
Fuel Filter Could be clogged need new one.
In tank Fuel Strainer
Low Fuel Pressure

I believe your Problem is directly related to physical fuel feed. Have you tried resetting your ecu to see if a relearn would help your fuel trims?

if youve done all that id take an uneducated guess and say it might be your front O2 Sensor because I think when the maf sensor is unplugged the ecu just tries its best to keep the car doing whatever your pedal is demanding without taking air volume into account and will adjust fuel feed based of AFR readings.

[Vanalex]

Previous Owner had this problem (Never told me) but masked it by letting air bleed out after turbo so it would counter the air accounted for from the MAF Sensor for example MAF sensor would read X amount of air and before I fixed the Air Leaks it would get around 3/4 of that accounted for air but after fixing all the air leaks it was getting full Air into the engine and ran lean because the Cold Air Intakes pipe width was greater than factories so it wasn't scaled for it. I'm a Bit sad that the 2 subies I ever bought I got screwed on and there wasn't even the least bit of honesty from either of them but anyway its mine now and forever and wont be touching much. Thanks to everyone for their help.