The problem first started when going to work one morning. the MIL light came on and wouldn't go out. The car drove fine no problems all the way to work. Coming home later that day there was no MIL so I thought it to be a one off and left it like that. Over the next week it would intermittently come on, but no adverse affects to the performance. Until one morning the car would not start.
On ignition, revs rose to about 3k then fell down to 500 then dropped off and stalled. I started back up again and revs fell down to about 100 then slowly rose to about 600-700 and started to idle ok except for a bad misfire every second or so. Lightly revved engine (to about 3k) and again the revs dropped to about 50 (nearly touching the pin), the whole car shook before the revs rose again to normal idle.
I checked all my spark plugs, wires and checked the vacuum lines, but was unable to find anything wrong. The car was serviced only two months prior. At this point, I decided to find out what the ECU thought the problem was by checking the Diagnostic Trouble Code, which I found to be Error 41 - Primary Heated Oxygen Circuit, Circuit Malfunction. Driving over to my garage to get the pros look at it and it cut out on me three times (while stopping at junctions, revs went down to nearly zero and stalled). They diagnosed the same problem and swapped out the whole sensor.
The ECU uses this sensor to calculate air/fuel ratio, so no wonder why it kept cutting out!