My 1992 Jetta 8v 5-spd idles at about 2000-2500 RPM when it's cold, but within a few minutes it drops down to around 1600 RPM. At times, I'll get off the highway and the RPMs will be back up around 2000. My gas mileage has gone down considerably; from 31 MPG+ to around 25 MPG, and I lost power. I just changed the oxygen sensor, and I think it helped with MPG and power, but it now idles higher!
I don't know enough about cars to know what this could be. All I know is that these problems literally occurred overnight (a cold night, though). Maybe the bad oxygen sensor slowly built crud up somewhere?
If anyone can help me, I'd love to have my old car back. Thanks. By the way, it's at about 86,000 Miles.

 

have u checked ur Throttle position sensor? i dont know a whole lot about VW's but i had the same problem on a previous car and that fixed it..