I had recently replaced the starter on my 97' Nissan Altima. I took of the air filter assembly to get to the mounting bolts for the starter. After putting everything back together after getting the new starter on I noticed a hose that was not connected to anything. I looked for half an hour for where it had come from. I tried just running the car without hooking it up to anything and the car idles really bad and sometimes it just shuts right off. I tried driving and I would have it around 3,000 RPM and it would drop down to 0 and shut off. The hose appears to be coming from the transmission (not sure, its on the engine on driver side of car). I read posts saying it was the transmission breather hose and it doesn't need to be connected to anything but my car never did this before and I had never noticed a hose not connected to something. Any ideas would be much appreciated.

Well, we can narrow down the oil and gas pumps. What about the air hose? I mean that IS the part you took off to get to the starter. Is the engine exceedingly hot or clunky when it dies?