Diagnosing Datascan Graph For R33 Gtr

[acediac]

Wondering if anyone can help me diagnose my datascan logs.

Car is a series 1 R33 GTR, totally stock including air box.

Fuel filter has been changed within the last 5000km.

Iridium plugs 13000km ago.

I'm getting an occassional stumbling on very light throttle.

I've logged some data with datascan, enclosed. To view a

graph of it, if you don't have datascan, you can pull it into

Excel as a CSV file, and graph the relevant points.

(File was saved as .txt because forum would not allow .log)

I've also enclosed a screenshot of part of the data.

In the screenshot, as indicated by the checkboxes,

top graph is RPM, AFM1, Speed

bottom graph is AFM2, Throttle, Timing

As you can see at the vertical line in the graphs, the car

is under very light throttle, constant 40kmh and both the

AFMs are cycling like crazy, and the A/F ratio is going

cycling between lean to rich very quickly.

I've already cleaned out both AFMs with electrical contact

cleaner. At first I thought one of the AFMs would be having the dry

solder problem, but surely not both at once? Is there some other

factor which could be causing this cycling? The rest of the AFM parts

of the graph look ok, I think?

Assuming the AFMs aren't both stuffed (it would be quite a coincidence!),

could it be some kind very mild surging happening which is causing

the air in the AFM to accelerate and decelerate really quickly, giving

those readings? If so, what could be causing the mild surging? Injectors?

I know about the AFM repair post, and I'm able to resolder the AFMs, but I'm

just not keen on opening and ruining the two nice and original AFM boxes without

some better proof that both are misbehaving at the same time! Surely if it was a

dry solder problem they would not give the exact same readings at the same time.

Just looking for someone with an experienced eye who can share ideas. Let

me know if there is any other data that I should log. Supported datascan fields are:

Register 0 active - CAS Position (RPM) MSB - supported

Register 1 active - CAS Position (RPM) LSB - supported

Register 4 active - Air Flow MSB - supported

Register 5 active - Air Flow LSB - supported

Register 6 active - Air Flow RH MSB - supported

Register 7 active - Air Flow RH LSB - supported

Register 8 active - Water Temp - supported

Register 9 active - O2 Sensor - supported

Register A active - O2 Sensor RH - supported

Register B active - Speed - supported

Register C active - Battery - supported

Register D active - Throttle - supported

Register 11 active - Intake Air Temp - supported

Register 13 active - Digital Register - supported

Register 14 active - Injector Time MSB - supported

Register 15 active - Injector Time LSB - supported

Register 16 active - Ignition Timing - supported

Register 17 active - AAC Valve - supported

Register 1A active - A/F Base - supported

Register 1B active - A/F Base RH - supported

Register 1C active - A/F Base SL - supported

Register 1D active - A/F Base SL RH- supported

Register 1E active - Digital Register - supported

Register 1F active - Digital Register - supported

Register 21 active - Digital Register - supported

Register 22 active - Injector Time RH MSB - supported

Register 23 active - Injector Time RH LSB - supported

Thanks!

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