...out, is it a sensor? My 1990 525i BMW idles irratically when I first start it, then after two minutes or so it evens out. The check engine light pops on and off, but then goes off completely when I give it gas. I was told that it may be a sensor near the thermostat. Does anyone know if it could be a sensor, and if so what is it called and where is it located exactly?

Have you had the o-rings checked on the injectors? maybe once they reach a temp a tight seal is created. Your mechanic should have a check list for that age bmw. hope this helps. Any codes on the computer?