Rough idle

Hi. I've got a 95 Ford Probe 4 cylinder with manual transmission. The car has been idling rough after warming up (rhythmic vibration, sounds like it's running rich). It idles at a constant 5 rpm with no stalling (I'm leaning away from the IAC valve as the problem, which I did clean). The engine timing is ok.
Check Engine light comes on sporatically, so I did a computer scan and got the codes:
11 and 112 (intake air temp sensor)
17 and 172 (oxygen sensor)
2 (crankshaft position sensor)

Questions:
1) I looked down by the crankshaft pulley and I can't see any crankshaft sensor mounted. My Haynes manual (all 1993-2001 Probe, 626, MX6) says "early models are equipped with one CKP sensor mounted in the distributor. Later models use a CKP sensor mounted on the front of the engine next to the crankshaft pulley in addition to the sensor in the distributor." Could/does "early models" apply to my 95 4 cyl Probe and there is no sensor below?
2) Could a bad oxygen sensor cause a rough idle?

Note: I switched the air intake temp sensor with a spare I had kept from another Probe (probably good) and the engine continued to idle rough.

Thanks.