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R33 GTS-T revs go up and down with contant throttle

fried_bride

By fried_bride,
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fried_bride Rookie

fried_bride

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Hey guys,

I've recently installed a greddy style front facing plenum, FMIC, 80mm throttle body and oil cooler. I started the car up and it idles normally... good start.

Unfortunately, when I gave it some throttle, the revs build then drop and build then drop. Not good. I'm getting fault code 55 "ALL OK". Could anyone shed some light on what I should look at to get this sorted?

fried_bride Rookie

fried_bride

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On 03/11/2021 at 4:11 PM, GTSBoy said:

What does your ECU tell you that it is doing?

Please tell me that you're not trying to run this on a stock ECU.

Yeah I am running this on a stock ECU. The way I was looking at it is that the stock ECU would be able to cope with the difference in airflow being that everything else is stock.

Do you reckon this is the culprit?

GTSBoy Grand Master

GTSBoy

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The reason I wanted to know you weren't trying it on a stock ECU is that changing to a really big TB is something that requires that you have a good handle on the mechanical and electrical condition of all the other things that matter, like the idle control motor. If you're doing it on a stock ECU, like everyone else who has ever done that before and had troubles (which is a massive percentage of all such examples) then you're flying blind, because you don't even know if your idle control system was workin before and you sure as hell don't know now and unless you have a decent Consult device or Nistune in the ECU (which you would have already used to find out what was going on if you did) you have no way of looking inside to see what it is doing.

Whereas, if you had an aftermarket ECU, even if it was Nistune in the stocker, you would know whether everything was working or not because you would have put the effort into making it work when the ECU was set up. And you'd be able to look inside and see what was happenign with the idle control.

The fact that pulling the TPS steadied the idle means that the ECU is now no longer using timing to try to control the the idle speed, which suggests that the idle control valve is not properly functional. You've quite possibly also got a large vacuum leak somewhere, or maybe the large TB is not closed enough to give the IACV enough scope to slow the idle.

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fried_bride Rookie

fried_bride

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On 03/11/2021 at 10:07 PM, GTSBoy said:

The reason I wanted to know you weren't trying it on a stock ECU is that changing to a really big TB is something that requires that you have a good handle on the mechanical and electrical condition of all the other things that matter, like the idle control motor. If you're doing it on a stock ECU, like everyone else who has ever done that before and had troubles (which is a massive percentage of all such examples) then you're flying blind, because you don't even know if your idle control system was workin before and you sure as hell don't know now and unless you have a decent Consult device or Nistune in the ECU (which you would have already used to find out what was going on if you did) you have no way of looking inside to see what it is doing.

Whereas, if you had an aftermarket ECU, even if it was Nistune in the stocker, you would know whether everything was working or not because you would have put the effort into making it work when the ECU was set up. And you'd be able to look inside and see what was happenign with the idle control.

The fact that pulling the TPS steadied the idle means that the ECU is now no longer using timing to try to control the the idle speed, which suggests that the idle control valve is not properly functional. You've quite possibly also got a large vacuum leak somewhere, or maybe the large TB is not closed enough to give the IACV enough scope to slow the idle.

Copy that mate! You are 100% correct. I ordered a Consult connector yesterday because I realised that I can't get very far if I don't have any way to query what the engine is doing.

Did you watch the video I posted? The idle was fine. I was getting issues when the throttle was open. Do you think that could have been due to the ECU doing a calc on fuel based on the volume of air expected through the stock throttle body using the TPS; and now that I have a bigger TB the calc would be off and result in running lean? I don't know if that is how it works but it was just the idea I had before disconnecting the TPS.

GTSBoy Grand Master

GTSBoy

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On 11/4/2021 at 6:07 AM, fried_bride said:

Did you watch the video I posted?

No. It won't load.

On 11/4/2021 at 6:07 AM, fried_bride said:

Do you think that could have been due to the ECU doing a calc on fuel based on the volume of air expected through the stock throttle body using the TPS; and now that I have a bigger TB the calc would be off and result in running lean?

No, the ECU doesn't give a stuff about the TB. The air flow meter is at the other end of the inlet tract, and that's where the air flow is measured.

If you're having trouble with the throttle open, it's starting to sound like the TPS isn't right.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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Many issues there, some I can see:

  • Stock ECU
  • AFM & pod filter
  • Reversion from intake pipe
  • Stock BOV deleted & using a AFM

Easiest fix, throw the stock ECU and AFM into the bin, install a proper speed density ECU.

fried_bride Rookie

fried_bride

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On 04/11/2021 at 9:01 AM, GTSBoy said:

No. It won't load.

No, the ECU doesn't give a stuff about the TB. The air flow meter is at the other end of the inlet tract, and that's where the air flow is measured.

If you're having trouble with the throttle open, it's starting to sound like the TPS isn't right.

Fair enough haha she was a beefy sized vid.

 

Thanks for the help mate!

fried_bride Rookie

fried_bride

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On 04/11/2021 at 9:20 AM, Dose Pipe Sutututu said:

Many issues there, some I can see:

  • Stock ECU
  • AFM & pod filter
  • Reversion from intake pipe
  • Stock BOV deleted & using a AFM

Easiest fix, throw the stock ECU and AFM into the bin, install a proper speed density ECU.

Copy! Any suggestions on an ECU? Been looking at a Power FC or one of those Haltec Plug and Play bad boys, but this is my first time doing all this stuff so I am very unsure.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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It's 2021 lol... please do not install a PowerFC, also you'll still need the AFM with the PowerFC and the way you've set everything up, a PowerFC will still give you you idle and stalling issues.

Just get a Haltech Platinum Pro Plug-in used if you can, great value and provides all the features you would need. If you have money and decide that one day you'll go tits out then get a better ECU that supports DBW, strain gauge input, etc.

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fried_bride Rookie

fried_bride

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On 04/11/2021 at 9:59 AM, Dose Pipe Sutututu said:

It's 2021 lol... please do not install a PowerFC, also you'll still need the AFM with the PowerFC and the way you've set everything up, a PowerFC will still give you you idle and stalling issues.

Just get a Haltech Platinum Pro Plug-in used if you can, great value and provides all the features you would need. If you have money and decide that one day you'll go tits out then get a better ECU that supports DBW, strain gauge input, etc.

You're a legend mate. Thank you very much for the advice.

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