Rb26 Idling And Rev Issue

[mr_rbman]

So after my car being off the road for 6 months finally got her booked in to be tuned Tuesday next week.

Finished a few small mods and maintenance issues and last night I did my coolant.

Only real modification's worth noting for this topic are:

-removed aftermarket fuel rail and FPR in place of going back to stock.

-installed recalibrated 'Nismo' AFM's after having Z32's.

-removed 'Apexi' pods in place of going back to stock airbox.

Now I'm getting the dreaded poor idle, running rich and it won't rev over 2500RPM.

So after a search this all points to AFM's and the soldering inside (my units are virtually new though (refurbished) so I would like to think this isn't the issue)

The only thing I can think is that when re-wiring the standard plugs back in I've possibly mixed up one of the wires? If I recall there was two wires the same colour...

I've attached the best drawing I could find googling but naturally I don't read Japanese.

does anyone have a better standard wiring diagram for the standard RB26 AFM plug?!

...Or does anyone have any other thoughts on what else could possibly be wrong?!

[Ben C34]

Did you adjust the tune for the different afms ?

[mr_rbman]

Hi Ben

It has a Nistune ECU and was tuned with the standard RB26 AFM's (was installing Z32's until I realised they don't mate up to std airbox)

So I was under the impression that going from the standard units to Nismo (equivalent) items it obviously needs tuning but would still be driveable or has the Nistune ECU picked up that these are different units and decided to crack the poops with me?!?

[GTSBoy]

Nistune hasn't "picked up" anything. The Nismo AFMs are the same physical size as the RB26 units but scaled the same as the Z32s. Consequently they are reading completely the wrong voltage relative to the amount of air that is flowing through them (compared to what the original AFMs would read with the same air flow). The ECU doesn't know you've changed the AFMs and is trying to run the engine according to a different amount of air than is actually flowing.

[kingtube69]

Nistune hasn't "picked up" anything. The Nismo AFMs are the same physical size as the RB26 units but scaled the same as the Z32s. Consequently they are reading completely the wrong voltage relative to the amount of air that is flowing through them (compared to what the original AFMs would read with the same air flow). The ECU doesn't know you've changed the AFMs and is trying to run the engine according to a different amount of air than is actually flowing.

Agreed - Was just typing this as well until it popped up that you replied.

[mr_rbman]

Ah thanks guys, makes sense now it's been pointed out.

In this state would you drive the car to the tuner (approximately 10kms) or have it towed?

Cheers!

[GTSBoy]

Do you have a Nistune license? If so, you could go in and rescale to suit the different AFMs. Otherwise, I would not drive it. Without engaging my brain too thoroughly, I would expect fouled plugs and possibly fuel in the oil.

[mr_rbman]

nah no Nistune licence.

ye I reckon I'll get it towed to be on the safe side.

It was definitely running rich while I was bringing it up to temperature doing the coolant.