Engine/diagnostic trouble

[jed]

Ok now this all started with the check engine light coming on,I went to a local
foreign auto shop they found a code for a o2 sensor (bank 1 sensor 1) they
drove it apparently to reset the light there's a note from the tech says
code pending in computer P1178 well I got it back drove home (10miles)
no problems that was friday today I go to start it battery's flat well thats a bitch never happened before battery's 3-4 years old O well check the alternator
output it's 14V little higher then I'd like but it's charging so I head out and it seems ok at first but when I go to stop it wont idle the tech reads 1500rpm and
by the sound it's right so I figure maybe it's trying to charge the battery?
well I get to where I'm going 15 min drive and when I park same thing wont idle
I check the pedal it's up all the way and after 1 min it idles 700rpm-ish so I tap
the gas pedal it shoots up to 2000rpm bounces around 1500rpm for 10-20 secs
and returns to 700rpm I repeat it a few times it does same thing every time so
now I want to try and figure out what can/might cause this any advice would help tremendously.