Frustrating problem with 940 dying randomly. Only dies shortly (1-3 miles) from a dead start. This is summer time in Tennessee. 90 degrees. Car will restart after a few minute rest. Like the old time vapor lock.

On diagnostic LED I get 223 (signal missing from idle valve error) and 132 low voltage error. I have removed and cleaned idle valve which looked very clean and seemed to be operating smoothly. Cleaned contacts. I replaced pressure sensor. I ran a can of injector cleaner through and throtle body looks good (sprayed cleaner anyway). Fuel pump was replaced somewhere in last 10k miles (used car, not totally sure of date) and fuel filter looks brand new...still shiny..so I suspect stlling problem is persstient. I have looked at ground wires, checked battery voltage at load, cleaned terminals, etc. looked at vacum lines, checked most of the codes on the computer identified in Chiltons manual (Pump relay indicates good).
Clear the codes and then after it dies (randomly) I get these same two codes.

Where to look next? What could be causing this combination of errors. Perhaps coicidnetally the spedo has become erratic. Replaced sensor with junkyard part and didn't get any better, maybe worse. Could these be related?
Any and all help greatly appreciated.

Dear dfeew9,

Hope this finds you well. If the idle air control valve (IACV) has failed, the car will be hard to start: as soon as the accelerator is released after start-up, the tachometer will plunge to zero, and the engine will die. Thus, if the car runs for 1-3 miles, and dies while your foot is on the accelerator - instead of when you're stopped at a light - I think you should check:
- the fuel pump relay (white plastic rectangle, on the main relay block, second row, driver's side of the row).
- the radio interference suppression relay, aka the fuel injection relay, a very dark brown/black rectangle, 2" (50mm) tall, mounted on the inner fender, between the ABS unit and the battery.

If these relays are factory-original, they don't owe you a penny. Even so, you may be able to repair them.

These relays - as with most in the mid-1990s cars - have solder joints on their circuit boards. These joints can develop micro-cracks, that break the circuit. These cracks can be far too small to be seen with an unaided eye. They can be closed by re-flowing the solder, with a 25-watt soldering iron. If the tip is touched to each joint, so that the solder liquefies (changes from dull gray to shiny silver), any micro-crack will be cured.

High ambient heat - plus the heat generated by normal operation - may cause a micro-crack to open up, cutting power to the fuel pump or to the injectors. The engine, starved of fuel, will die. When the temperature drops, the crack closes enough to allow the engine to re-start.

It is well to carry spares for these relays. No tools are needed to change them, although a screw-driver will help you to remove the under-radio storage tray (in the center front console), improving access to the main relay block.

Hope this helps: please post back with your findings.

Yours faithfully,

spook

Spook,
Your counsel is appreciated. I bought a new fuel relay and it seems to have helped, but candidly the car hasn't been driven much so I'm not declaring victory over this intermittent problem. I had tested the relay when I wnet through the diagnostic tree int he Chiltons manual and it tested good, but since it seemed to be a common root cause to everything I read, I sprung for the $35. I may resolder the old one. I was wondering waht the failure mode was. I opened it us and the contacts looked fine, so now I have a project. Now on to the erratic spedometer problem...(separate post). I didn;t realize owning an old VOlvo was a total immersion experience...
Regards and thanks for taking the time to help newbies like me.