[Jerr]

Hey friends,

I've been having really strange idle issues specifically on radiator fan kick that I can't seem to diagnose. I tried a new tune which sort of band-aided the problem, but I didn't have this issue before on my tune which leads me to believe it's a mechanical or electrical issue.

The behavior: when the car is hot and idling and the thermostat calls for fans to kick on, the idle dips from the normal ~900 to 450 (almost stalling) and back to 1300, then back down to 450, over and over until the fans turn off. When the fans are off, everything goes back to normal. While this is occuring, I can see STFT jump around from -2 to +20 and AFR going all over the place. Interestingly, if I manually turn on the radiator fans by turning on the AC, the car compensates properly and idle sits at around 1000 stable. This problem is able to be replicated.

Things I have replaced/done:
-Checked for vacuum leaks (tune logs also show none)
-New battery optima yellowtop
-Checked that alternator is working (battery is charging properly)
-New OEM MAF sensor
-New OEM front O2
-New OEM PCV Valve
-Throttle body is still fairly new since ~1 year ago
-Air intake/filter parts completely cleaned
-Fresh flash of stable tune from when car was originally "dialed in"

I noticed in the logs that right as the fans kick on and before the idle actually dips, the MAF reading in g/s jumps up from 2.5 to about the 4.8 range, and the MAP reading goes from .3bar (stable idle) to .46 which is counterintuitive as the RPM is dropping, therefore the boost should be lower...?

Does anyone have any ideas of what might physically be wrong? I figured maybe fans drawing too much amperage but the same issue would also persist when AC was turned on, right?

Thanks all!