Transmission or O2 problems
 

I have a 2004 Hyundai Santa Fe 3.5L with 230k.

ever since I had the car there has been a slight slip when changing from 2-3 gear (exactly at 20mph). My car would make a banging sound if I kept trying to accelerate. My work around has basically just been timing the shift and once I let off the gas it goes into third without slipping. A few months ago, I had to change my starter and to get to it I had to remove the o2 sensor. After, I put everything back, the car didn't slip or anything for months until recently again which led me to believe that was the cause. I replaced the one o2 sensor and it's still slipping, even worse now.

on top of that, on rainy or damp days trying to drive is a nightmare. My engine makes like bubbly sounds and has major issues accelerating which causes a lot of jolting. Also, when I try to accelerate there check engine light comes on but goes away once I let off the gas. This only happens on damp days until the car is warmed up. I've had it looked at a few times and apparently no one sees any issues with my car (of course when I take it it's always driving perfectly).

any suggestions?? Thanks!!

Well,try basics first.Dampness,and electrical problems may lead to think,there is something going on with ignition system:bad,old wires-sparking somewhere else,so not all high voltage goes into the spark plugs.Inspect really close all spark plugs,and better yet-install brand new NGK Platinum.NGK only,nothing else.Inition coils may be defective,also,so is condition of ignition wires-burnt end tips surface connections-arcing over the long time may deteriorate connection pretty bad.When you install ignition wires-use dielectric grease,to minimize future arcing by sealing against water;that will help some. As for transmission,i I've hard,that reprogramming transmission may help.You may find somewhere with GOOGLE how people try to do it without visiting mechanics.I I've got manual transmission,so my inerest,and knowledge about automatic trans. is rather limited.