Rough idle, no power down low

[ExergyDestruction]

I have an all stock 93 240sx. The car has a rough idle and does not make any power under 2800 rpms. I get a code 55 but I think it might be the O2 or the engine coolant temp sensor. The symptoms are as follows.

The car idles rough when cold started but makes power. It doesn't feel as strong as it did when it ran well, but it is better than when warm. As the car warms up the idle becomes worse and doesnt make any power under 2800 rpms. Above that it gets better but still not perfect. Once the car is warm, the idle smooths out and feels like it does when the car isnt warm and it still doesnt make power below 2800. The car also sputters until around 2800 and gets only a little better above that. It sounds like an f'in volkswagen when I drive around just not as loud. Finally, there is also the smell of propane (not raw gas or rotten eggs or anything like that) every once and a while. It is completely random and I am not sure if it is connected to the other problem(s).

I tested the O2 by using the ecm self test and it came out ok. I also tested it by unplugging it but the car ran the same. Not sure if the car switches to limp mode if it is unplugged though or if it does go to an open loop. I have yet to test the coolant temp sensor but I will do that right now. Any help would be appreciated. Sorry for the long post but I want to make sure I included everything thats wrong with the car. Thanks

[ExergyDestruction]

I checked the engine coolant temp sensor and it gave good readings, 5V and about .8ohms with the car not fully warmed up. Then I checked the maf. There are only three wires/three connectors inside the harness and the fourth connector slot (labeled #1 in the fsm), where the voltage should be checked, is empty. WTF do I have a SOHC maf on my DE? How would this work (obviously it isnt) and would I have to change the whole harness? Nistech, Rev D, anyone have any suggestions?

[NISTECH]

you are looking at the connector wrong. leave it plugged into the airflow meter. If I am right one wire is black with white tracer one wire is black and one is white. use a paper clip or a T-pin and probe the wires from the back of the connector. the blackwith white tracer is you voltage should be 12v the black is your ground and should measure less then .02 volts and you white is your signal should be around 1.3 volts at idle warmed up.

edited

[ExergyDestruction]

thanks. sorry for being an idiot in the last post. I read somewhere that there were 4 wires on a DOHC. I went back and checked the fsm after the fact and everything checked out so i am not sure what it coudd be. Could a leaky/bad injector causes this problem? Thanks.

[NISTECH]

did you ever check your timing?