2002 Mazda 323 stalls when fans kick in

2l engine FSZE 14 MPFI. Customer complaint was that when the fans kick in the revs drop really low and sometimes it even stalls.
No fault codes. Removed throttle body and cleaned minor build-up, idle control valve looked clean. After scoping duty cycle to the idle control valve I noticed that when it goes to stall the duty cycle spikes to 100% (shown in attached images). Also after doing further tests trying to get it to play up the engine light came on and I got a code P1523 "VIC solenoid". Fitted a new VIC solenoid (controls swirl valves) and cleared the code.
Also decided to fit a new idle control valve because one pattern made it look like it was perhaps sticking making it go to 100% duty cycle.
It's still doing it and actually cutting out now and then.
I've just scoped the oxygen sensor and notice it goes lean each time the fans kick in? One of the attached pictures shows this.
One of the guys suggested setting the base idle by bridging out some pins and adjusting the idle screw but that makes no difference and I don't see how it would with an intermittent fault.
Any suggestions on where to go next?

This is the injection when it happens, you can see the injection time increasing to try and compensate(?)

I scoped the coils and at one stage the vehicle felt like it was running on two cylinders. I unplugged coil 1 and there was no change.
As soon as I plugged it back in again the engine ran smooth. This time I scoped the trigger and common coil positive and you can
see coil 1 switching drop away, even though it's getting its trigger.

Hi Desmond,

I think idle control valve at 100% means also only that PCM is trying to increase revs and avoiding engine stall (the same you described about injection pulse width).

About coil picture, note that coil pulses never stopped, which means for me that voltage drop, is due to low rpm (generator stopped charging).

Have you checked any fuel delivery issue?

guafa wrote: About coil picture, note that coil pulses never stopped,

Look at the picture again. In the first part of the image for every yellow (coil 1 trigger) pulse there are two voltage drops
at the coil feed, one that lines up with the trigger which is coil 1 firing, and one between the yellow pulses which is coil 2
firing. When the revs drop there is no longer a voltage drop for coil 1 firing which is when the engine is running on two
cylinders.

Desmond6004 wrote:

The coil trigger signal for cyl 1 drops in amplitude the same time when the voltage drop disappears for cyl 1. what does cyl 3 and 2 coil trigger signal look like? Are those trigger signals also dropping low in amplitude?

No, the signal remains constant for the other coil.
I did notice that when I unplugged coil 1 the signal goes right up to 12v - that was when I was trying to prove a point that cyl 1 wasn't having any effect on the engine running.
I was actually quite surprised how easily the engine ran on 2 cylinders.

Oh yes. Now i understand your point about coil picture.

Have you noticed that when trigger pulse drops to something below 3 volts, is the same moment when voltage drops stops?

Maybe trigger pulses don't have enough power to trigger that coil.

Like jreardon asked, are the trigger pulses for cyl 2 and 3 in the same voltage level?

guafa wrote: Have you noticed that when trigger pulse drops to something below 3 volts, is the same moment when voltage drops stops?

Maybe trigger pulses don't have enough power to trigger that coil.

Like jreardon asked, are the trigger pulses for cyl 2 and 3 in the same voltage level?

The pulse for the other coil is the same level.
With a new coil fitted everything is fine so I imagine perhaps a failing transistor is pulling the voltage of the trigger pulse down rather
than it being a weak pulse not triggering the coil properly.

Whats is happening to amps draw and battery voltage, I am wondering if there is a seriuosly excessive amps draw from the fan coupled with a battery or fuse box issue.

Andy.MacFadyen wrote: Whats is happening to amps draw and battery voltage, I am wondering if there is a seriuosly excessive amps draw from the fan coupled with a battery or fuse box issue.

As mentioned the fault has been fixed - it was a coil dying.
I imagine the fan kicking in just added an extra load on the engine to make it idle worse when it was happening.