Engine cutting out of hard left turns

[foolio]

This is sort of a Hail Mary. I haven’t done much research yet so forgive me. Just want to get this question out there to try and salvage tomorrow’s track day. Will be hitting the googles now. Anyway, car is a dedicated track car, 2003 SMG coupe. Only engine mods are headers and an Epic race tune. Brand new NGK OEM plugs. Been running great all weekend (Friday, today) until the second to last session of the day. When I am in a hard left hand turn, the engine starts cutting out. Have about half tank of gas. The harder the left, the more it cuts out. Once I straighten up, it clears up. Happens consistently on every left turn on the track. Fine in right turns and straights. I have had fuel starvation before and in my experience that is more of what I would call a “soft” cut out where I just lost some power, like the engine is starving. This is like a light switch. Also, it’s a stutter type cut out...the engine doesn’t stall. Just a bunch of hard bucking until it clears up. I feel it’s electrical. I checked the engine ground on the passenger side and it is fine. Battery is new. Checked alternator connections. I feel like something is shifting and shorting out...I don’t know, that’s just a guess. Happy for any info. Unfortunately since the car is a dedicated track car and I trailer it, i decided to leave it there tonight. I am going to check grounds for the coils tomorrow. Thanks for any ideas!

[eacmen]

Fuel starvation would be for hard right turns at least in the US. Not sure if RHD cars have fuel pump on opposite side tho.

Could it be traction control related? Do you have DSC on?

maybe sign of failing fuel pump?

any codes?


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[foolio]

Thanks @eacman for your ideas! I do not run with DSC on. And you’re right about the fuel starvation. When I’ve had it of course it’s been hard right turns. Plus, I never really get it unless I’m down below a quarter of a tank. I love my Epic tune but, Here’s one thing I don’t like... For some reason, it won’t throw codes. If I want to see codes, I have to put the original tune back on. Not sure why but that’s kind of annoying. I even got this “technique” from Epic. So, I think the first thing I do tomorrow besides checking all the connections to the coil‘s is to put the old tune back on and go out and run my first session. Then, I’ll see what codes I have. I am going to bring a new set of spark plugs and a used set of coils in case I need to swap some things around. I suppose it could be a failing fuel pump after 17 years but the car does only have 38,000 miles on it. Granted, about 10,000 of those are hard track miles.

Fuel starvation would be for hard right turns at least in the US. Not sure if RHD cars have fuel pump on opposite side tho.

Could it be traction control related? Do you have DSC on?

maybe sign of failing fuel pump?

any codes?


Sent from my iPhone using Tapatalk

[eacmen]

I don't have any actual experience with this but putting my armchair mechanic hat on, it seems that the fuel pump would have to work harder pumping fuel against the G forces of a left hand turn since the fuel pump is on the right side and the fuel line is on the left side.


But this theory could be total BS.


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[foolio]

I don't have any actual experience with this but putting my armchair mechanic hat on, it seems that the fuel pump would have to work harder pumping fuel against the G forces of a left hand turn since the fuel pump is on the right side and the fuel line is on the left side.


But this theory could be total BS.


Sent from my iPhone using Tapatalk

I’ll take anything at this point lol 😂

[Slideways]

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/49964-how-does-fuel-make-it-from-the-lh-side-of-the-tank-make-it-to-the-rh-side

[foolio]

https://nam3forum.com/forums/forum/m...to-the-rh-side

This is very interesting. Go to look at that tomorrow for sure. Thanks!

[TexaZ3]

Just spitballing it here - injectors, fuel filter, ignition coils, vanos pressure?

[foolio]

Ok first of all thanks everyone for scratching their head with me on this one. I’ll spare the troubleshooting details because ultimately it was all moot due to something simple. After spending a while looking around and testing (thanks for the link Slideways) I came up empty. Even tried a full tank of gas. In any case, a buddy was looking over it and noticed the intake boot had slipped off the intake but if you weren’t looking closely, it wasn’t obvious. There was no gap visible. I suspect that on left turns, the engine was leaning over ever so slightly and opening the gap letting in a massive amount of unmetered air and the ECU responded by cutting fuel or spark immediately or something. So, I re-fit the hose and tightened the clamp and all was well the rest of the day. Good excuse to buy solid motor mounts I guess! 😁😁😁

[Da Jemster]

Glad you sorted it out. RockAuto sends out a monthly newsletter and I remember an article similar to your situation. His was some type of wiring issue that would falter on the "bad turn" but reconnect when he straightened out.

[CrookedCommie]

Ok first of all thanks everyone for scratching their head with me on this one. I’ll spare the troubleshooting details because ultimately it was all moot due to something simple. After spending a while looking around and testing (thanks for the link Slideways) I came up empty. Even tried a full tank of gas. In any case, a buddy was looking over it and noticed the intake boot had slipped off the intake but if you weren’t looking closely, it wasn’t obvious. There was no gap visible. I suspect that on left turns, the engine was leaning over ever so slightly and opening the gap letting in a massive amount of unmetered air and the ECU responded by cutting fuel or spark immediately or something. So, I re-fit the hose and tightened the clamp and all was well the rest of the day. Good excuse to buy solid motor mounts I guess! 😁😁😁

I'd go poly so you don't have to weld the front subframe.