I have an 83 240 volvo with the single wire O2 sensor. My car has about 215,000 miles on it and ran great until I changed the O2 sensor. The old sensor was old, and I replaced it for that reason. I first replaced it with a cheap acdelco universal model, and ran the car for a couple hundred miles with no problem until it randomly began idiling at 2500 rpms. Suspecting the problem was the new O2 sensor I had recently installed, I shut the car off and disconnected the lead coming from the sensor. I started my car up again and immediately the car stopped idling at 2500 rpms, but rather it idled slightly below normal at just under 1000 rpms, and slighlty rough. The next day I spent a little extra money and got the Bosch universal O2 sensor and installed it. Upon start up my car ran perfectly for approximately 25 minutes and maybe 10 miles, until it began idling at 2500 rpms again. Now I'm driving the car with the sensor disconnected until I can figure out what's wrong with it. I would have tried putting the original O2 sensor in, but I destroyed it when I was trying to yank it out.

Please help if anyone knows what's wrong with my car.

Matthew