IW STi Forum banner
1 - 20 of 30 Posts

· Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
As the thread title stated – 2012 STI new build that is surging at warm idle

Build list

Outfront V4 block with ½ inch arp head studs
Professionally machined heads to accept:
GSC Stage 2 EJ257 Billet Camshaft Set Dual AVCS (Intake and Exhaust)
GSC Subaru EJ Series Chrome Polished Intake Valve - 37mm Head (+1mm)
GSC EJ series Chrome Polished Super Alloy Exhaust Valve-33mm Head(+1mm)
GSC Power-Division high-pressure CONICAL Spring set with Titanium Retainer

Grimmpeed TMIC
Grimspeed overtake bb500 turbo
Grimmspeed intake
Grimmspeed 3 port boost controller
Grimmspeed unequal-length headers
South Bend Clutch Endurance Stage 3 Clutch / new flywheel
Up-pipe with Tial 38mm EWG
ID1300 injectors
Stock TGV housings/functionality
Radium FPR, fuel rails with 6AN fuel lines after FPR in parallel deadhead config.
DW440 fuel pump wired with fuel pump controller
removed the secondary air pump
Invidia high-flow cat downpipe
NGK LFR7A spark plugs gapped at 028
using ECUTEK hardware for tuning/ monitoring

I’m still in the break-in and it's surging at warm idle.
At first, I figured this was a tuning issue, so I sent off some logs, and 2 new maps later with MAF adjustments, we are here in the same boat.
Checked all the vacuum lines, and low and behold I thought I found the cause, the turbo to boost controller hose had a small hole. Replaced it, and now I can idle once warmed up, but if I press the gas at all, it starts to surge.
To further clarify, after starting, and letting it warm up, it does idle just fine.

As soon as I use the clutch and gas (small rev <2000) or start to maneuver it out of the garage, it has the surge, and sometimes stalls out.
here is a video of the surging STI warm idle surge

once in a while when it stalls out, I get a P0017 for crankshaft position correlation bank 1 Sensor B, but I assume that has something to do with the stall – code clears and doesn’t come back until it surges and stalls a few times

figured it could be the front O2 sensor in the header - its a replacement from oreillys auto parts. Unplugged and issue persists.

When I removed the stock fuel rails + lines under the intake manifold, I no longer had the purge hose to connect. I capped off all 4 hoses on the evap / purge solenoids (or valves) that are connected to the wiring harness behind the power steering pump/alternator thinking maybe I had a leak there.

I have chatted with my tuner, and they are saying vacuum leak or incorrect fuel pressure ( I can't seem to get the Radium FPR without the vacuum line connected down below 48 for some reason before the adjustment screw comes loose)

If you have read this far, thank you for getting through most of my long-winded thought process. Please let me know if I can provide any other information.

Because I have reset the ECU, do I need to let it idle while warm for a while to relearn?

To the brighter minds here -still a vacuum leak or am I going down the wrong rabbit hole?

I ordered a cheap smoke tester off Amazon, ill have to see how that goes.
I also ordered replacement Intake manifold gaskets (gaskets between TGVs and the heads are new, but I reused the intake manifold gaskets as they looked great) and a new throttle body gasket is on the way as well.
 

· Registered
Joined
·
126 Posts
I had an issue like this. (Similar surging)

I had busted my baro sensor when deleting the secondary air injection pump.

You can check this by seeing what the pressure reads when the car is off. If it's working, it should be atmospheric pressure 14.7

The reason this screwed with my car is when it breaks. It can read the minimum sensor limit of idk 7psi or something.

This then results in the ecu applying afr compensation. That the front o2 sensor will try and fix... = surging up and down

I tried things similar to you before realizing this was my issue. Vacum leak, map and maf sensor test ect

Sent from my SM-S901W using Tapatalk
 

· Registered
Joined
·
58 Posts
from svc manual. they call the fuel pressure regulator a "pulsation damper". one section has removal instructions and another section (big picture) has pulsation damper A and pulsation damper B shown as (3) and (24) in the diagram.
nothing in the troubleshooting section mentioning surge :/ not sure but maybe could be related.

Font Material property Parallel Art Paper


Font Map Line art Drawing Art
 

· Registered
Joined
·
56 Posts
If you're using the stock fuel pump hanger there is a restriction at the venturi pump, which would explain why you can't lower the fuel pressure.
If your injector scalar is set for stock fuel pressure of 43.5psi you'll have problems scaling your MAF.
You can test this by setting your base pressure to the minimum possible + ~9psi to account for vacuum at idle, so round up to 60psi.
Adjust your injector scalar accordingly and scale the MAF, you should be able to tell if that was your issue.
To actually fix it you can hack up your fuel pump hanger and replace the venturi with one from Radium. Or replace the whole hanger, Radium has one of those too.
 

· Registered
Joined
·
19 Posts
Discussion Starter · #11 ·
I did modify a stock fuel hanger to get the dw440 in, thank you for explaining that part.

I bought a second stock fuel hanger to modify to fit the dw440 - ill look into what it takes to replace the venturi or just replace the whole hanger

Im at work today - so I haven't been able to get home and check timing - or baro sensor readings. Will be able to reply tomorrow with those.
 

· Registered
Joined
·
2,965 Posts
Iduno I think I would be looking into that crankshaft position fault. Crank sensor issues can cause many problems for all kinds of cars. Even if you have a vacuum leak, or even a fuel pressure related problem...it shouldnt be causing a crank sensor position fault.

Its possible you may have more than just 1 issue here.
 

· Registered
Joined
·
19 Posts
Discussion Starter · #16 ·
Finally got my Venturi jet pump kit - and got it installed. It's definitely a bit of a modification to the stock fuel hanger, but success - I can now adjust fuel pressure.

I validated timing, and that the baro pressure is correct (per the method above).

After getting the assembled fuel pump hanger back in the car, I was able to easily adjust the fuel pressure. it's able to idle probably due to the fact that it goes instantly into limp mode with the p0017 error.

Jay11STI - I do have multiple issues at this point, so I'm going to investigate the sensor issue described by the dtc p0017.

Subscribed to alldata diy - which presents the data a little easier (for me at least).

I'm going to drain the oil and swap out the referenced sensor - I'll give another update here with what I find.
 

· Registered
Joined
·
126 Posts
Are you able to post a log ?

  • timing
  • rpm
  • afr learning 1
  • afr correction
  • afr learning 3
  • front o2
  • injector duty cycle
  • avcs timing (idk what this one is called in the logger)

Also, I know you found a vacuum leak before, but have you tried a boost test ? (You unconnect all the pcv systems and cap those spots. Then, pressurize the system. Also, leave your oil cap off). This method guarantees no leaks

Sent from my SM-S901W using Tapatalk
 

· Registered
Joined
·
19 Posts
Discussion Starter · #18 · (Edited)

· Registered
Joined
·
2,965 Posts
I have not tried a boost test - I can get some caps and pressurize the system.

I replaced the passenger side cam sensor - and the DTC code has not come back (after 2 idle sessions).


Here is a current log: datazap.me | nepix | Log 1674194398
if you just want the standard csv, let me know.


Is there a chance that my idle is just set too low?
Has the idle corrected itself after replacing the sensor? After something like that, I think it would have been good to clear faults and reset the ecu. Let it relearn everything all over again.
 

· Registered
Joined
·
19 Posts
Discussion Starter · #20 ·
I disconnected the negative terminal for 30 mins and gave it another try. It reacts exactly as what's captured in the log linked above. The relearn procedure did not correct the issue.

Everything works fine during initial start / warm up once warm it does idle well for a bit ( feels a little rough under 900 rpm I assume due to the cams) then starts that surging after minute or so.
 
1 - 20 of 30 Posts
Top