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Neo Fuel Problem

JonnoHR31

By JonnoHR31,
in Engines & Forced Induction

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JonnoHR31 Grand Master

JonnoHR31

Posted
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Just finished putting an auto er34 rb25det into a manual hr31, wired it up and got it running yesterday. It started straight away and idles like a dream, except the ecu isn't putting in any extra fuel when pumping the throttle, making it UN-drivable.

I've been over the TPS wiring several times, its got power and at the ECU plug the signal wire reads .45v when closed and 4.0-4.1v at WOT so the ECU is getting the TPS signal and it's working as it should. As far as i know the TPS signal is the only thing the ECU uses for throttle pump injection so this has me stumped. Does anyone have any ideas why this wouldn't be working and how to fix it? Possibly something I've missed in the wiring? Or is there something else than can cause the same symptoms (stabbing the throttle causes revs to drop until the ECU picks up the extra flow via the AFM) that I'm missing?

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https://www.sau.com.au/forums/topic/406040-neo-fuel-problem/
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GTSBoy Grand Master

GTSBoy

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You need to get a consult connection going so you can see what's going on.

You're also going to need to Nistune it if you want to be able to get around the lack of traction control and ABS that the ECU expects to see. Otherwise it will throw codes about the TCS/ABS comms and the TCS throttle position sensor.

JonnoHR31 Grand Master

JonnoHR31

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Consult isn't really possible at the moment unless I can find someone local with one, might have a scope around the WA section.

There was always going to be error codes but I was under the impression they wouldn't affect the actual running of the motor? I've taken it for a test drive and apart from this throttle hesitation it drives perfectly and doesn't have any cuts under full boost or anything.

GTSBoy Grand Master

GTSBoy

Posted
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Is it all still connected? If the ECU can't see the TCS TPS it'll have a fit.

The ECU still chucks a wobbly even if it is connected - if there is no TCS computer present to make the throttle do the close-open dance when the ignition is switched on. That's one of the error codes that comes up. Nistune can mask it.

And this stuff can still cause hassles even if you get past all these little annoyances. The Nistune blokes worked out that if you do not have the TCS stuff working, when you up the boost/flow and get up to a reasonably high power level, then the ECU starts pulling shenanigans that feels like a rev/boost limit, and can't be tuned out. It is possible that Stagea ECU images do not have that problem (as they do not use TCS).

GTSBoy Grand Master

GTSBoy

Posted
Posted

Got it sorted, had the ECU boost sensor hooked up to the manifold, moved it to the intake and now it's running fine. Weird.....

That'll do it. I just checked my engine. That sensor is connected to the crossover pipe immediately adjacent to the BOV. I guess it is not supposed to see vacuum.

Hanaldo Grand Master

Hanaldo

Posted
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The ECU still chucks a wobbly even if it is connected - if there is no TCS computer present to make the throttle do the close-open dance when the ignition is switched on. That's one of the error codes that comes up. Nistune can mask it.

And this stuff can still cause hassles even if you get past all these little annoyances. The Nistune blokes worked out that if you do not have the TCS stuff working, when you up the boost/flow and get up to a reasonably high power level, then the ECU starts pulling shenanigans that feels like a rev/boost limit, and can't be tuned out. It is possible that Stagea ECU images do not have that problem (as they do not use TCS).

Spot on. It's very annoying :glare:

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

One of the wires was broken but it didn't make any difference.

Got it sorted, had the ECU boost sensor hooked up to the manifold, moved it to the intake and now it's running fine. Weird.....

Can u Please explain this a little more?

Had a 34 come in that had the same symptoms as urs after another mechanic did a headgasket. I had to disconnect the boost sensor to stop it trying to stall on takeoff. Such a simple little thing

JonnoHR31 Grand Master

JonnoHR31

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It seams to not like seeing vacuum, so just make sure it's hooked up somewhere before the T/B and it should be fine.

Thanks for the suggestions everyone.

Hi Jonno, i know its off topic but why did you get rid of your RB30DET and put a AUTO RB25DET neo into your HR31?

Sold the car to my younger brother, put a stocker neo (it's now manual) in for him and I'm selling my engine seperately along with a lot of other stuff.

StevenCJR31 Veteran

StevenCJR31

Posted
Posted

It seams to not like seeing vacuum, so just make sure it's hooked up somewhere before the T/B and it should be fine.

Thanks for the suggestions everyone.

Sold the car to my younger brother, put a stocker neo (it's now manual) in for him and I'm selling my engine seperately along with a lot of other stuff.

ah cool . . . are you using the auto ECU that you got with the motor? could be causing issues if you are?

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