Civic EG

having trouble with my idle.it would idle very low when at a stop fells like its about to stall out and suddenly it will surge up and go back to normal..this all happen a week after valve adjustment then the car would run rich and blow out black smoke but when the check engine lite came on it would run smooth which was CEL 1 primary o2..got the valve adjustmnet done again and i was told that the last person who did the adjustment made it tight but only by a fraction of a tiny bit..the idle problem went away car ran nice but later on came back then check engine light came on for CEL 1 again o2 sensor the car run nice..took off the o2 sensor it was black covered up with carbon and i run my car like this for almost 6 months..i decided to leave the o2 sensor unplug and it runs and drive smooth without idle problem better trothle respond and less bogging..im thinking my o2 sensor is dead but was told it could be the tps..so now im debating whether i buy an o2 sensor or the tps..which one would most likely fail? dont wanna be disappointed to find out the problem still exist after spending money..wasnt the first time it happen but trying to stay away from it..any suggesttion
the motor is a jdm b16 sir2

Most likely to fail is the O2 sensor. I'd replace that just because. They're not that expensive, and they're easy to replace, so why not?

TPS isn't all that easy to repalce. If you want to get one from Honda, you have to buy a whole new throttle body. Omnipower, Blackworks, and a few other companies make and sell the B-series repalcement TPS. I got mine from Omnipower for $80 I think (it's been a few years). Hell, www.hondapartsunlimited.com sells the Blackworks TPS. And they're a Honda dealership in Phoenix.

thank you very much ill go ahead and buy an o2 sensor and ill let you know if anything changes....but would a bad o2 sensor affect my idle that much it will make it idle low almost to a stall..?

I'm not 100% sure on that question, but a failed O2 sensor will send the ECU into auto-rich mode where it basically dumps fuel into the engine. Which would be the reason you're getting black smoke out of your tailpipe.

It could also be the TPS sending an incorrect voltage to the ECU as far as the low idle goes, but low idle can be a number of things from TPS, to IACV. But that wouldn't explain the excessively rich running.