Just a couple weeks ago, I bought myself a used 2003 Chevrolet Venture Warner Bros. When I test drove it, everything worked completely fine. I drove it around that day and it wasn't until later that evening after stopping at a store, when I turned it on, after its initial turn on and it would go to idle, it stalled. Luckily, I lived around the corner so I would have to turn it on, put it into drive immediately, and it would drive until I slowed down and stalled out.
I got it towed to a shop the next day, thinking maybe it was clogged fuel injectors because I had used a fuel treatment maybe 2 hours before everything started happening. They took the codes (mainly saying the engine was misfiring) and replaced my Mass Air Flow Sensor, spark plugs, wires, and Idle Air Control. She was still running rough, but they were able to get my van to where it wouldn't stall out if I kept my foot slightly on the gas at stops. They also showed me that, when plugged in and unplugged, the O2 sensor was stuck in an open loop. I've had the same issue on my last car, but it never made it run like that.
Being my only vehicle, I brought it home and scheduled to bring it back the week after so they could "rewire my o2 sensor" since they said that was the main issue. After having it for another 24 hours after, they said I needed to bring it back again. It seemed to be running even better this time where I wouldn't have to play with the gas at stops. It was only when it would start up and idle, it would idle rough and try to stall out unless you gave it enough juice in park til it would start to idle gently.
Due to finances, I haven't brought it back again yet, but in the last week, it doesnt chug and run rough once I turn it out, and drives fine, but now it will either start idling high when its parked occasionally and when I first drive it, it sounds as if it can't figure out what gear it needs to be in and bounces for the first 5 minutes.
If anyone has an idea of what I could check to figure that out and I can avoid bringing it to the shop and racking up a fat bill, that would be awesome