Jump to content
SAU Community

Neo Fuel Problem

JonnoHR31

By JonnoHR31,
in Engines & Forced Induction

 Share

Recommended Posts

JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

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?

Link to comment
https://www.sau.com.au/forums/topic/406040-neo-fuel-problem/
Share on other sites
GTSBoy Grand Master

GTSBoy

Posted
Posted

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

Posted
  • Author
Posted

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
Posted

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
Posted

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

Posted
  • Author
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.

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?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • GTSBoy
      R34 GTR running rich and noisy turbo coincidence

      By GTSBoy · Posted

      Put a fuel pressure gauge on it. Replace the turbos. Probably completely separate issues.
    • Dose Pipe Sutututu
      R34 GTR running rich and noisy turbo coincidence

      By Dose Pipe Sutututu · Posted

      CAS maybe?
    • silviaz
      Recomended Coolant For Gt T R34

      By silviaz · Posted

      What copper washer do you guys use on the bleeder bolts? The existing one I have I had no idea where to find it in a local store, I did buy some online but that are only 1mm thick whereas my old one is 2mm+ thick and when I put the new washer out and squeeze the top radiator hose I can hear a bit of air but not with the old one. Does this matter? The new one doesn't leak, but the inner diameter is a bit loose whereas the old one threads on the bolt.
    • donut_kng
      R34 GTR running rich and noisy turbo coincidence

      By donut_kng · Posted

      Howdy all, after being out a few weeks ago on a spirited drive in my GTR I have 2 issues that oddly have appeared at the same time. Whilst accelerating quickly through the gears all of a sudden i’ve lost power at the top of third gear (below redline around 6000rpm) for no obvious reason.    From that point onwards the car has been running rich on idle, won’t really rev under load without a ton of black smoke and the odd backfire, and dying as a pull up to a set of lights unless I keep the revs up around 1500rpm. In addition when shutting down the car that same night (I was 10 minutes from home) I noticed one of the turbos was significantly noisy on wind down when shutting off the engine. After letting the car cool down overnight it starts up fine, although once it gets to temp the revs start to creep up and down, the exhaust is darker than it should be and it also sounds like it’s running rich (fat note) I’ve put a new set of plugs in it - no change, the old plugs all seemed OK with two of them being somewhat richer/fueled up than the other 3 with 1 being borderline. I’ve smoked tested the intake system via the front of the Turbos, found a split vacuum hose going to the factory boost gauge sender, which I have since replaced.  Also found another leak on the gasket coming off the rear turbo outlet, have also replaced this. After fixing both of these leaks - still have the running rich issue. I’ve also tried another pair of AFM’s - no change here After pulling off the front turbo intake pipes, there is obvious shaft play in the front turbo, which now hisses loudly on light revvs although I can’t see why this would make the car run funny even under idle. I’m curious to know why it’s running rich before I potentially replace/rebuild turbos. The car is completely stock <50,000kms  other than an exhaust. Oil and coolant are all clear. I haven’t bothered with coil packs as it looks like they won’t be the issue due to condition of the plugs. Any help appreciated as I cry myself to sleep!
    • Rezz
      R34 4 door side skirt identification

      By Rezz · Posted

      No probs at all. I used to love trying to dig up obscure info for those in need where possible going back 20+ years on SAU.  I did have another look and couldn't come up with any closer match. I'm leaning towards those skirts in your first pic are custom fitments, cut down/extended or from another car entirely and modded to fit an R34 sedan. I would've thought someone in Japan had them and taken a photo at some stage over the last 2 decades but there's nothing. Someone out there must know surely.
×
×
  • Create New...