R33 GTR running either crazy lean or rich...need urgent help!!

[judasentinel]

I have a 1995 R33 GTR, which is fairly stock, except the usual exhaust and intake pod filters.

Here is my issue and this has me stumped. A year ago, I had started a thread here about seeing something called a VACS (Variable Airflow Control System) come pre-installed on my car when I bought her. The VACS is conneced to the ECU with 5 wires - two go the AFMs , one goes to ground, and the other two are soldered into the ECU circuitry, away from the pinouts. I knew that thing was useless, so people on here suggested I take it out. I disconnected that VACS from the ECU (just unplugged it), and the car starts to run crazy rich - 10.3-10.6 afr on idle.

Then I tried to use a stock R32 GTR ECU, with the O2 sensor ground connected so that it runs on the R33 GTR loom (as suggested by Nistune), and the car starts off, but idles extremely lean - around 17.3-17.8 afr. I am confused as to why it would be.

Asking for help from anyone who might have some ideas about the causes. The AFMs are stock and so are the injectors, at least from what I can tell. What throws me off is the inconsistency between the R32 and R33 ECUs, where one is causing extreme leanness, and the other is causing extreme richness. Shouldnt there be a semblance of similarity in the two, as they both run RB26DETT off of the same sensors, and shouldn't have opposing effect.

There are also these images that I want to share, of my R33 GTR ECU's internals, for anyone who might be able to tell me if the ECU is stock (in terms of the R580 chip) or it seems to have been modified with a chip or anything else. The first image shows the ECU itself with the chip, and the second one shows the wiring that goes from that stupid VACS into the ECU. I disconnected the VACS from the plug you see on top left corner of the second image and that is when the car runs extremely rich. With an R32 GTR ECU, the car runs extremely lean.

Any help will be greatly appreciated. Thanks, all.