Surging revs at idle - R33 GTR

[R33GAS]

I recently purchased a 1995 R33 GTR V-Spec. It has a flex tune, making about 370awkw. I use E85 exclusively. Has upgraded injectors but not sure if the fuel pump is still stock or not (which I’m thinking might be the issue?).

As per the video, it has an intermittent issue of surging/pulsing revs at idle, which will eventually stall if I don’t manage the revs with the accelerator. Won’t usually happen during a cold start, but after it’s warmed up and I make a stop during my journey and turn off the engine, then restart, it rears its head.

Can also present when driving, as I slow down/stop, then sit at idle, it will stall if I don’t keep on top of it. 

It has no trouble during acceleration by the way.

Any help would be appreciated, thanks.

 

[GTSBoy]

More likely to be faulty IACV than anything else. In this case "faulty" mostly being dirty to the point of sticking open/shut when it is supposed to be moving. The ECU keeps cranking on it until it responds, and then it responds too far, hence the unstable idle and possible stalling when stopping.

It's only like the 2nd most common question on here with literally thousands of threads to look through.

I don't like the chances that the original fuel pump is doing 370awkW on E85. That would be outside the bounds of possibility. More than 99% likelihood of it being upgraded.