1999 S70 Immobilizer stopping car after starting

[GrumpyOldMan]

I had an issue with my 850 for the last 6 months.
I thought it was a fuel issue that started after I replaced the fuel filter.
The car would either start then stall within a second, or wouldn't start at all.
But, it would always start within 3 attempts.

I replaced the fuel pump and return line on the engine.
Later I removed and cleaned the contacts on the immobilser ring.
None of which helped.

One night 6 months later, as I was driving along, the auto started banging, hunting, neutralizing.
The next day I could start the car, but as soon as I put it in gear it would thump into gear and stall.

The cure for every fault was the ignition wafer.
As soon as I replaced that, every single fault was cured.
Hard to start, stalling, bad gear changes, chattering relays, lamda and gearbox lights.

I don't know if this is your problem or not, but its an easy fix if it is.