Here's the symptoms:

Check engine light keeps coming on.
Codes say either temperature sensor or fuel injection problem. All else ok.
I'm replacing the temp sensor, but don't think that is the problem.
Pulled out air mass meter, and he large hose (air intake) between it and the engine has oil in it. I'm thinking this may be messing up the air mass meter.
I checked the flame trap on crankcase vent. Not clogged.

Does the oil fill cap provide venting for crankcase?
Why would have oil backing up in the air intake?
Thoughts apprecated.

 

crankcase ventilation on a 240 is done via a 'oil seperator box' on the intake side of the engine, its below the intake manifold, behind the idle air controller, and forward of the EGR if you have one.

there's a 'flame trap' on the hose out of this that plugs up, also the whole thing plugs up if neglected, and when that happens, oil can get blown out all sorts of places. I'm not sure offhand where this vents to on a 1990 240, on my 1992 740 turbo, its vented into the big air pipe between the MAF and the turbocharger.

what codes specifically are you getting?

 

Unless you have a large amount of oil in the tube, I doubt that it is causing the codes. Each of my 240s have a small amout of oil that accumulates in the bottom of the tube. Not more than a few drops though.

Basically the crankcase ventilation draws air from the crankcase into this tube (and into the throttle body). The air in the crankcase has tiny oil droplets that will condense in the tube and accumulate at the bottom.

As Pierce asked, what codes are you getting?