odonnell

Usually these sensors don't suddenly fail, they start to go out over time (they're analog). In Doug's case, it's a wiring fault.

JacRyann

Engine always dies on 85.5+ cars when engine coolant-temp is unplugged. Tested on '85.5 na and '86 & '88 951.

Also see what happens when you disconnect AFM.

Dougs951S

The car starte and idles pretty well actually with the afm unplugged. I havnt tried unplugging it while it was running. It obviously idles better with it plugged in.

gtroth

Yeah, this surprises me too. NTC II, the engine temp sensor, I also thought was only used for cold enrichment (NTC I, the air temp sensor in the AFM, is what's used in the lambda loop).
Worse case failure should just cause it to run rich. I don't think a ridiculous reading would cause it to run ridiculously rich- no reason to engineer it that way. Of course I suppose the evidence to the contrary means I don't understand it right.

Is it possible you are already running rich and this just pushes it over the edge? If NTC I were reporting colder than reality, that would cause the DME to command more fuel than the air mass needs...

Raceboy

If you have failed coolant temp sensor and need to start and run the car you can unplug it and short the pins in the plug, this way DME thinks that engine is at the operating temperature and runs properly. But it will be very difficult to start the engine once it cools down and ambient temps are less than 15-20c (you need starting fluid to aid, brake cleaner also works, or just plain gas into the intake).