2 months, 3 check engine lights, 4 replaced sensors... what's wrong?
 

i'm driving a 1995 maxima GXE, and in the past 2 months the "check engine light" has come on a few times, and each time i've brought it in to have it fixed.

a few years ago we changed the oxygen sensor under warranty, and that was that.

but starting this summer, we've changed the (i'm not sure of the technical terms):
- temperature sensor
- oxygen sensor
- exhaust sensor
- "cold engine" sensor (due to rough idle with a cold engine in the mornings... as if the automatic tranny was going to stall)
- water tank cap

is there something wrong? our car is about 9 years old, and is this normal to have all of these sensors to fail all at once? i searched and read that the alternator may cause the oxygen sensors to fail if the alternator is failing (our car suffers from the high pitched whine).

any help would be appreciated :)

Old age, things start to ware out.