2002 Dodge Stratus Slow/no start, CEL, P0171

Engine Performance problem
2002 Dodge Stratus Front Wheel Drive Automatic 100k miles

I took my car in for tune-up (new sparks, wires). The car drives much better now. But driving out of the shop I had a CEL which they tested and claimed was the result of 2 bad O2 sensors, which they diagnosed from a P0171 LEAN BANK 1 code. I did not have the sensors replaced.

The next morning and every day thereafter I am unable to start the car unless I try 3 or 4 times. The car shudders and shakes each time and the engine won't catch. Finally the engine finally catches but it still shudders and shakes for a few seconds until there is what sounds like a surge, and then suddenly the engine runs smoothly and there is no shaking or fear of stalling. The CEL comes on immediately and stays on.

My mechanic uses the computer to check for errors and to test the engine. He says he finds no vacuum leaks. There are no MAP sensor errors. The fuel pump immediately reaches 52 and then stays between 55 and 60, which he says indicates no fuel pressure problems. He did find an O2 sensor code finally, after the temperature reached about 142, so he replaced it, but my problems remain the same and are seemingly worsening a bit over time. For example, I used to be able to start it right up if I had driven it 8 hours before, but now it takes a couple of tries to get going in the afternoon now.

I don't know if this has anything to do with the problem (he immediately said No) but I have noticed once in a great while that when I park the car I can't always push the gear shift all the way into park, so I end up turning off the car first, THEN putting the car all the way in park and removing the key. (Since I do everything out of habit, I usually have turned off the car a millisecond before I realize I didn't quite reach the proper position). It's like it bumps into something and doesn't quite make it all the way. This happens intermittently, however, whereas the other problems are daily. Maybe there's no connection but I figured I should mention it.

Is my mechanic missing something? Does the dealership need to look at this? Could it be the timing belt or fuel pump- two things he's saving until last? PCM? ECT? Stuck-open thermostat? He seems stumped and I fear being stranded somewhere.