OK, I know I posted a response to this last night... or maybe I closed the window.

Anyway:
Top photo is a late-model 740 EGR temp sensor - it's in the EGR valve body.
Middle photo is an earlier-model EGR temp sensor - in the EGR intake(?) tube.
The two different sensors have different threads and opposite functions - one has resistance that goes up with temp, one the opposite.

I think the bottom photo is next to the IAC... is it?
I also think that looks a lot like the connector for the late-model EGR temp sensor. There is a distinct pair of twined wires for it and the plug looks correct too. You can see the wire in the bottom left of the bottom picture matches the wire connected to the sensor in the top picture.

Has someone swapped out your ECU? Someone (cough, cough, Kruse-Lucas on Tully Ave in Modesto cough) put a 92 ECU in my car and swapped out the temp type to match it. I know this because the sensor went bad and I had to replace it and had to figure it out. A few sensor exchanges in the mail led me to find out the newer style one was worth like 350$ new from the dealer and not available in aftermarket.
If you have an older model ECU and want to sell your newer sensor I'll give you my old (read: broken) sensor for a plug. For free, I think shipping was like two dollars. And it can be sent "general delivery" to your nearest post office if you're concerned about giving out addresses.

Good luck,
Will

PS: one of those sensors is non-functional and just acting as a plug.


--
1990 740 Turbo, on its way to stock specs, maybe beyond

great detail in pictures

Hey Greg,


I am pretty sure that the first photo is of the EGR temperature sensor. The second photo appears to be related to the EGR system, but I am not sure what it is. Perhaps someone with more experience will be able to help. Not totally sure about the third either. There are two temperature sensors for the engine beneath the intake manifold. The one closest to the front of the car is for the temp gauge, and the second one closer to the firewall is for the fuel injection and ignition. Maybe this is the one that's unplugged in the third photo? The MAP sensor is located on the drivers' side strut brace and is fastened down with a couple of screws. It has a vacuum hose that exits from its underside and connects to the intake manifold. Its a hard plastic hose with rubber ends. They often crack and fail with age. The oxygen sensor is just in front of or on the catalytic converter. You car appears to be equipped with the Regina injection system, so the oxygen sensor is special and a 'universal' one cannot be used in its place, as its electrically incompatible. Check out the FAQ about the engine sensors, this link takes you to the section regarding the EGR system.

http://www.brickboard.com/FAQ/700-900/EngineSensors.htm#EGRValve

Regards, Jon 'Uncle Olaf'