It is now summer here in Arizona and my daughters 940 Volvo is acting up. She will be driving along fine - tach drops to zero car stops. After a few minutes, sometimes a few hours it will start and be fine again.
Fuel relay related, etc is NA here - once it stops it appears electrical. Took it to my fav mechanic of 15 yrs and it is one of those crappy intermittent problems, that are hard to find. After being on your forum and doing much, much reading... could this be the ignition amplifier module and is there a way to confirm it? 1994 940