[NEED HELP] EJ205 stalls after cold start — AFR at 14.7, fuel pressure good

Chev · 05-06-2025, 04:14 PM

Hey everyone, I’ve been stuck on this issue for weeks. My freshly built EJ205 will crank, start, sometimes rev up, but it always dies out shortly after — even though the AFR is perfect at ~14.7.

Tuner is away and now recommends I get someone else to look at it, but I can’t afford to tow it or pay for a shop diagnosis right now. I’ve done everything I possibly can solo and am hoping someone here can help me make sense of it.

***128295; Build Overview
Engine: EJ205 w/ fresh rebuild

Injectors: Cobb 1050x (professionally cleaned & tested – passed 100%)

Fuel Pump: DW 255LPH (brand new)

Turbo: Arashi TD05H-16G

ECU: Stock 16-bit WRX ECU, tuned using ROMRaider

Intake: Cobb SF Intake system (MAF, post-MAF, box, etc.)

Exhaust: Nvidia 3” turboback, Tomei UEL header + up pipe

Other Mods:

Grimmspeed 3-port EBCS

DIY TGV deletes (OEM housing)

EVAP system fully deleted (firewall line vented to atmosphere)

***9989; What I’ve Already Checked/Fixed
AFR sits at ~14.56–14.7 at startup

Fuel pressure:

42 psi in accessory mode

Jumps to 50 psi during crank

Settles at 43 psi after engine dies

Smoke tested intake and vacuum system (from both turbo inlet and brake booster) — no leaks found

Brake cleaner test (sprayed around gaskets, TGVs, caps, etc) — no idle change or AFR spike

Throttle body replaced (old IACV was sticking — fixed)

Throttle cable properly tensioned

MAF is brand new Denso OEM

Injector pulse width shows ~2.7 ms during logs

No CELs, IAM remains stable

***10060; The Actual Problem
Car starts, might rev up to ~2k or even 3k with just a light tap of the throttle, then immediately dies

Idle dips low and gets rough, even when it tries to stabilize

Tried starting with MAF unplugged ***8594; car wouldn’t stay on at all

Exhaust smells strongly of fuel after crank attempts (rich?)

Fuel pressure remains steady before, during, and after crank

Logs show good AFR, yet engine still dies like it’s fuel starved

Sometimes engine catches itself and revs back up before stalling, as if the ECU is trying to stabilize but can’t

***128269; What I Need Help With
Is there anything else I can test by myself without shop equipment?

Could this still be a tuning issue, even with AFR looking normal? Enrichment? Afterstart decay?

Does the rich exhaust smell contradict the 14.7 AFR reading?

Could this still somehow be a small air leak even if AFR is fine and smoke test passed?

Any thoughts, ideas, or weird cases you’ve seen before would mean the world right now. I can’t afford shop help but have a laptop, tools, logs, and time — just need direction.

I’ll upload all the logs in the comments if anyone’s willing to help review them.

Thanks a ton ***128591;

Also wanted to add, Could it be a bad Idle relearn from all the testing I've been doing?

Here are the logs they are public on my drive for you guys to check out.
https://drive.google.com/drive/folde...QF?usp=sharing

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Charlie-III · 05-06-2025, 10:23 PM

Have you tried an ECU reset? I typically just clear codes with an OBDII scanner, others do a longer battery disconnect, etc.
Have you pulled plugs and looked at them? If so, are they wet with gas, covered in soot?
What spark plugs and gap?
Is this COP (coil on plug) or ignition wires?
When it dies, does it start right back up, or does it need to sit?
Can you see realtime data? You should turn it on and compare ambient temp to ECT and IAT, they should be within a degree or so.
Is this fairly fresh fuel, or has it been sitting?

Chev · 05-07-2025, 03:30 PM

Quote:

Originally Posted by Charlie-III

Have you tried an ECU reset? I typically just clear codes with an OBDII scanner, others do a longer battery disconnect, etc.
Have you pulled plugs and looked at them? If so, are they wet with gas, covered in soot?
What spark plugs and gap?
Is this COP (coil on plug) or ignition wires?
When it dies, does it start right back up, or does it need to sit?
Can you see realtime data? You should turn it on and compare ambient temp to ECT and IAT, they should be within a degree or so.
Is this fairly fresh fuel, or has it been sitting?

Havent tried an ECU reset yet, It almost makes me think it might be a bad idle relearn. Havent checked plugs yet but they are brand new and it does fire up. I can reset codes on ecu and then disconnect for a idle relearn and see what that does.

Its OEM style coil pack to spark plugs, not ignition wire.

When it dies I noticed sometimes it wont start back up and then once I let it sit for a bit sometimes ill get a little longer of a fire up and what not, but the main thing I noticed is I tap the throttle and it literally shoots up to like 3k rpm which u can see in the logs. which is just odd, and still holds the rpm even once off the gas.

I can try to read the real time data, I am on from raider and ecu flash so it shouldn't be an issue. Fuel was sitting for like 3 months or so, but was fully drained during my rebuild process as the pump just kept priming on my old ecu, anyways I put in fairly fresh fuel like 2 weeks old at most.

If possible, please hit me up on my alt email, only dropping my alt email here cuz its public but, potentially, if possible maybe we can get a call going or something. Id really appreciate it as I'm so stumped out here
[email protected]

Chev · 05-07-2025, 03:31 PM

Quote:

Originally Posted by Charlie-III

Have you tried an ECU reset? I typically just clear codes with an OBDII scanner, others do a longer battery disconnect, etc.
Have you pulled plugs and looked at them? If so, are they wet with gas, covered in soot?
What spark plugs and gap?
Is this COP (coil on plug) or ignition wires?
When it dies, does it start right back up, or does it need to sit?
Can you see realtime data? You should turn it on and compare ambient temp to ECT and IAT, they should be within a degree or so.
Is this fairly fresh fuel, or has it been sitting?

Also to add, the plugged are all gapped to .028

mconnell · 05-21-2025, 02:59 PM

Not sure if this has been resolved, but fueling can get gunked up in lines, in filter or in injectors and present like this. Also checking spark cant help and then finally, if it never ran before like this on this tune, maybe just an issue with the tune. This thread is 2 weeks old though so maybe your tuner got back and fixed it

Chev · 05-30-2025, 08:25 PM

Quote:

Originally Posted by mconnell

Not sure if this has been resolved, but fueling can get gunked up in lines, in filter or in injectors and present like this. Also checking spark cant help and then finally, if it never ran before like this on this tune, maybe just an issue with the tune. This thread is 2 weeks old though so maybe your tuner got back and fixed it

Hey man actually tuner is stumped without the car in front of him no one can really find anything here I linked some more videos of me starting it but tuner hasn't really gotten back to me with something definitive. I could really use some help. I really just debating rn waiting to get back to work and than trying to bring it in somewhere which is like a stab in the heart here so if you think you can find anything here please lmk I can try the fuel lines checking em and stuff but here take a look at this please and lmk what you think. Im losing my mind over this.

https://drive.google.com/drive/folde...8J?usp=sharing

Gonna try to post on some other places as well. try to see if anyone else can help but I've posted in like 10+ different places but imma keep trying man cuz this is lowkey my daily so I want this fixed

Chev · 05-30-2025, 08:26 PM

Quote:

Originally Posted by mconnell

Not sure if this has been resolved, but fueling can get gunked up in lines, in filter or in injectors and present like this. Also checking spark cant help and then finally, if it never ran before like this on this tune, maybe just an issue with the tune. This thread is 2 weeks old though so maybe your tuner got back and fixed it

Also tuner assures me that this tune is good to go for a first start. This is what he uses on his other cars and has been adjusted to my mods as a first starting tune so he can than log and get me my full break in tune

jaxscuby · 06-05-2025, 01:52 PM

so you have ecuflash * romraider.
So open you rom file and check you injector flow scalar.
data log the maf (voltage & g/s)

from what your described it sounds like maf table needs to be tweaked.
but the AFR's you're reporting 14.5-14.7 sound almost impossible.

even stock AFRs have a wider range that..short & long term fueling.

screen capture ecuflash with your injector table and maf table (show the graph)

05-06-2025, 04:14 PM	#1
Chev Scooby Newbie Member#: 539462 Join Date: Oct 2024	[NEED HELP] EJ205 stalls after cold start — AFR at 14.7, fuel pressure good Hey everyone, I’ve been stuck on this issue for weeks. My freshly built EJ205 will crank, start, sometimes rev up, but it always dies out shortly after — even though the AFR is perfect at ~14.7. Tuner is away and now recommends I get someone else to look at it, but I can’t afford to tow it or pay for a shop diagnosis right now. I’ve done everything I possibly can solo and am hoping someone here can help me make sense of it. *128295; Build Overview Engine: EJ205 w/ fresh rebuild Injectors: Cobb 1050x (professionally cleaned & tested – passed 100%) Fuel Pump: DW 255LPH (brand new) Turbo: Arashi TD05H-16G ECU: Stock 16-bit WRX ECU, tuned using ROMRaider Intake: Cobb SF Intake system (MAF, post-MAF, box, etc.) Exhaust: Nvidia 3” turboback, Tomei UEL header + up pipe Other Mods: Grimmspeed 3-port EBCS DIY TGV deletes (OEM housing) EVAP system fully deleted (firewall line vented to atmosphere) 9989; What I’ve Already Checked/Fixed AFR sits at ~14.56–14.7 at startup Fuel pressure: 42 psi in accessory mode Jumps to 50 psi during crank Settles at 43 psi after engine dies Smoke tested intake and vacuum system (from both turbo inlet and brake booster) — no leaks found Brake cleaner test (sprayed around gaskets, TGVs, caps, etc) — no idle change or AFR spike Throttle body replaced (old IACV was sticking — fixed) Throttle cable properly tensioned MAF is brand new Denso OEM Injector pulse width shows ~2.7 ms during logs No CELs, IAM remains stable 10060; The Actual Problem Car starts, might rev up to ~2k or even 3k with just a light tap of the throttle, then immediately dies Idle dips low and gets rough, even when it tries to stabilize Tried starting with MAF unplugged 8594; car wouldn’t stay on at all Exhaust smells strongly of fuel after crank attempts (rich?) Fuel pressure remains steady before, during, and after crank Logs show good AFR, yet engine still dies like it’s fuel starved Sometimes engine catches itself and revs back up before stalling, as if the ECU is trying to stabilize but can’t 128269; What I Need Help With Is there anything else I can test by myself without shop equipment? Could this still be a tuning issue, even with AFR looking normal? Enrichment? Afterstart decay? Does the rich exhaust smell contradict the 14.7 AFR reading? Could this still somehow be a small air leak even if AFR is fine and smoke test passed? Any thoughts, ideas, or weird cases you’ve seen before would mean the world right now. I can’t afford shop help but have a laptop, tools, logs, and time — just need direction. I’ll upload all the logs in the comments if anyone’s willing to help review them. Thanks a ton 128591; Also wanted to add, Could it be a bad Idle relearn from all the testing I've been doing? Here are the logs they are public on my drive for you guys to check out. https://drive.google.com/drive/folde...QF?usp=sharing Registered users of the site do not see these ads.

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05-06-2025, 10:23 PM	#2
Charlie-III Scooby Guru Member#: 30669 Join Date: Dec 2002 Chapter/Region: Tri-State Location: USA, North NJ, 07456 Vehicle: 1998 Legacy 2.5GT Silver Sleeper BK, 5MT	Have you tried an ECU reset? I typically just clear codes with an OBDII scanner, others do a longer battery disconnect, etc. Have you pulled plugs and looked at them? If so, are they wet with gas, covered in soot? What spark plugs and gap? Is this COP (coil on plug) or ignition wires? When it dies, does it start right back up, or does it need to sit? Can you see realtime data? You should turn it on and compare ambient temp to ECT and IAT, they should be within a degree or so. Is this fairly fresh fuel, or has it been sitting?

05-21-2025, 02:59 PM	#5
mconnell Scooby Newbie Member#: 541113 Join Date: May 2025	Not sure if this has been resolved, but fueling can get gunked up in lines, in filter or in injectors and present like this. Also checking spark cant help and then finally, if it never ran before like this on this tune, maybe just an issue with the tune. This thread is 2 weeks old though so maybe your tuner got back and fixed it

06-05-2025, 01:52 PM	#8
jaxscuby Sammo Hung Moderator Member#: 10613 Join Date: Sep 2001 Chapter/Region: South East Location: N Fla / S Ga Vehicle: 2002 USDM WRX WRB	so you have ecuflash * romraider. So open you rom file and check you injector flow scalar. data log the maf (voltage & g/s) from what your described it sounds like maf table needs to be tweaked. but the AFR's you're reporting 14.5-14.7 sound almost impossible. even stock AFRs have a wider range that..short & long term fueling. screen capture ecuflash with your injector table and maf table (show the graph)