1994 Toyota Curren 3S cuts out when hot.

Customer complaint is that it cuts out when hot and "loses all electrics" which can mean different things with different customers
It can't be losing all electrics because he says it will crank and 'almost fire' but needs to be left to cool down before it will start again.
It hasn't done it in the workshop yet.
The spark plugs are old and have a 1.5mm gap. There is a flash code 21 "oxygen sensor circuit" and the heated circuit on the sensor is open circuit.
Before I go changing anything, and doubling the resale value of the car in the process, I'd like to see it actually fault as I have the oscilloscope on the ignition coil switched side and the ignition module input trigger as that could also be failing.
I'm wondering if the large spark gap and open heater circuit on the O2 sensor could produce a symptom where the vehicle does actually cut out when it's hot. [Idling is also rough]

I would start with the known problems and go from there. You don't want to have those as additional variables while you diagnose.

Nissan Technician

I would also check fuel pressure when it acts up, I had a 2002 firebird, and after 30 minutes of driving, the pump would overheat and stop pumping fuel. let it cool for 30 minutes and it would crank up and drive again for another 20-30 minutes. I drove it like this for a week or so, and changing the pump was the fix.

Thanks - this is one of those jobs that refuses to play up while in the workshop - or during a test drive which makes it that much harder.
Yesterday I removed the ECU and checked it for leaking capacitors and it looks like it had already been replaced.