Apexi Pfc Rpm And Idle Issues On R32 Gtr

[ocousins]

Hey everyone,

I have been living with a finicky and strangely behaving R32 for long enough and I thought I would probe your minds for some info on what my ignition issues might be.

First a description of the symptoms:

1. Apexi commander RPM display is very "noisy', "spikey" or "unstable". By that I mean that at idle the RPM will average 950, but instantaneously vary as low as 850 rpm, and up to 1100 rpm. This happens way too fast to be a wandering idle, it is something electrical. I am certain it's not due to instantaneous rpm changes due to big cams and a lumpy idle because the same behaviour occurs over all RPM. Even when I am cruising at 3000 RPM the commander reports a RPM that varies quickly +/- 100 RPM without me feeling any surging at all. Note that the stock tach is stable

2. THe commander reports a spark timing that is also just as unstable or " noisy" this will very +/- 2 degrees all over the map, including idle even though I have disabled spark control of idle speed and made sure to make all ignition cells in the area of idle the same number just to prevent my noisy rpm from causing the ECU to interpolate between ignition timing cells

3 While cruising and watching the 10 second live plot of ignition timing, I noticed that if I ever lift the throttle, the spark timing retards about 10 to 15 degrees for a second or two then returns to a nominal value as I decelerate. This got to be so bad that as i accelerated and would shift, the first 2 seconds of accel in the next gear would be boggy as the ignition timing would retard 15 degrees when i lifted throttle before the change, and stay down after the shift for a bit. I changed the Cam angle sensor (with another used one) and this remains, although not so bad as to affect the next upshift

My efforts to rectify:

A.The first thing I did was check that the coils and ignitor are well grounded and they seem to be (although I haven't added a ground kit)

B. I installed a different CAS. The spikey RPM remains, as does the unstable spark timing even at idle while ignition idle control is turned off. The short term ignition retard on throttle lift remains, but returns to nominal quicker

C. I figured it was EMF interference from either the ignition coils or injectors so to test this I pulled the fuel pump fuse, and removed the CAS but kept it plugged in. I then spun the CAS with a cordless drill. I expected to see a noisy RPM and then alleviate in by disconnecting the coils, ignitor, or injectors one by one. But I was surprised to see a rock steady RPM reading despite hearing all the injectors and plugs firing.

I am out of ideas of what to try next, the only variable I can think of that is left is the tolerance between the CAS and the Camshaft splines but I really hope to spare myself the cam change just for diagnostic purposes

has anyone experienced something like my problems? does anyone have any thoughts of what to do next?

I wouldn't care so much about this, but I am just about to purchase a Datalogit and I don't want erroneous rpm signals to cause an auto tune to be messing up with the wrong fuel cells