ok so i finally fixed everything wrong with my car but has a code for something about emissions controller idk how to fix it or what could cause it also planning to finish my 5spd swap but i would like to get this taken care of first

 

You fixed everything but you did not say what you fixed nor what the error code is. Is it a small evap system leak code? Check the evap lines to see if you have any cracked lines or pinhole leaks. My car had a small hole in the rubber line from the evap canister to the tank return pipe - located on the driver side - running along the fender well held in place by some clips.

It takes some systems a few cycles of running down the road at normal operating levels to fully synch up the PCM and in the meantime, you will get error codes spitting out. Changing the O2 sensors, the MAP sensor, the Crank Position sensor, the Cam position sensor, etc. etc. can cause what you are seeing and could be part of why you are getting the error code. In this case, you can clear the error(s) a few times while during this transition time. This assumes that it is not a critical system error code that can cause damage if you drive it. After you do this about 3 times, if you still get the error code, something with that system is most likely bad.

 

i replaced the o2 sensor and recently had a head gasket done motor has 18 k original mile on it

 

With only 18000 miles on the motor and you needed a new head gasket?! Damn! Either you got a lemon, a bad rebuild job, or you have been ******* the heck out of it!

The new O2 sensor and the PCM have to synch up - assuming you don't need the other O2 sensor replaced too - the error code should clear up after a few run cycles. If it don't, then you need to start checking out the other emission sensors - one by one - starting with the other O2 sensor. If your car is a 1995 model - you may also want to give a check to the MAP and MAF sensors. 1996 and up have only the MAP sensor.

 

its not a rebuild its original miles i had the factory plugs in it yet when i got the motor and trans it had 14k neons go at 18to19k when they came from factory my donor car was a 1999 plymouth expresso 4 door it was wrecked with 14k on n it and i bought the whole car for 300 bucks best deal ever i dont believe it had 14k miles i got real luck finding it it sat in the woods for about 3 years since it was wrecked with a tarp on it i pulled it to the garage got some oil and fresh gas in it and it fired right up