Your 1992 240:

OBD Socket 6 for the Bosch EZK ignition, code 2-2-4 indicates a faulty engine temp. sensor.

And your verified you have all codes from the EZK socket six and got only code 2-2-4?

Did you check socket 2 for the Bosch LH-Jetronic codes?

Do so. If you get one code, repeat so you get all codes using both sockets.

The http://www.brickboard.com/FAQ/700-900/ would suggest verifying both the temp sensor as well as continuity from the spade lug that connects to the temp sensor to where ever the hell that circuit terminates at the the ECU boxes.

You could check temp sensor impedance while on the car at cold and then, when safely connected so you don't burn yourself, when warmed up. I'm unsure, but when the fuel/ignition temp sensor has failed, it causes the fuel / air mix to go fuel rich. But I'm not sure, may go lean. Blame my dyslexia in so may ways and means subtle and gross. I may be getting K-jet and L-jet / EZK confused (Mr. Kotter!).

As many miles as you have, and being in Bohemia in NY-state would indicate possible corrosion among wire harness connectors and perhaps ground connections on the unibody. NY-state, like other Northeast and Midwest states, lay down eight tonnes of salt for every snowflake, so compensate for any wire harness corrosion problems at connectors and grounds to the unibody. (I'm repeating myself, yes?).

Questions?

cheers,

Luck.

Sleepy Volvo 240 Owner.
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Goodnight. Sleep Tight.