i have a 1993 gsr car with a ls/vtec that i just dropped in i had this engine in my car before but i took it out to change piston rings and bearings so i put it together and droped it in. i got it to start but it idles very low. when i open the throttle in neutral it lags a bit but it revs up nice above 1500 rpm but as soon as i put it in first gear the rpm drops instantly. If i stay at the throtle the car barely moves 5mph tops at wide open throttle the ecu throws code 20 i had this problem for almost a week and i havent had a chance to break in my engine. also i dont have my o2 sensor hooked up beause i got the wrong exhaust manifold that has the o2 bung on the front and its open manifold because it was also too short but im in search of the stock one. ive seen my friends car run without an o2 sensor and this never happen i think the o2 sensor itself wouldnt do this. I HATE CODE 20

I KNOW ITS A CHALLENGE BUT PLEASE HELP ME OUT!!!

 

Is it timed correctly?

Sounds like you're timing is off...

Especially if it was hard to start...