I am working on a 86 740 turbo 246,000 miles, the car will just stall when driving down the road. Just as if the key were shut off. I already replaced the hall sensor in the dist.,plugs,wires,cap ,rotor,good used power stage,maf,fuel pump relay,intake gasket. And the car will sometimes just die. When it is at idle it sounds like it has a miss. But when you drive it or rev it up all seems to run great. Also the temp gauge wil only read about 1/4 in stead of half when it is warmed up, but I do not think that would cause this situation. Any help would be greatly appreciated.Thanks

 

You replaced the hall sensor but did you inspect the hall wiring from the sensor all the into the harness as far as you can see? That wiring is of the disintegrating variety and is known to cause exactly the thing you describe.

 

Since you've already replaced quite a few things at least you know what it isn't. About the only thing left is the Hall sensor wiring as Lev has mentioned. There is the chance the ecu is bad but they can be had relatively cheap on eBay or turbobricks.com The 541 was the stock ecu, 591 the slightly better replacement Volvo used at the dealership for failures. $40 is about as much as I ever paid for the 541. 591's are scarce and unless you need an ecu that is easily chipped, I wouldn't bother. Obviously, the temp issue is thermostat, sender or gauge. The miss at idle could very well be a bad vac hose. Since they carry positive pressure under boost in a hotter engine compartment, they fail faster
than in an n/a car. I don't spend much time looking on my personal cars; I just trade out every single hose in the bay. I prefer using silicone hose, but that's just a preference.