Hi,
I have a 2003 NB that has air conditioning and noticed an issue last year. I forgot about it over the winter (daily driver) and then we started getting hot weather here in Oregon yesterday. The symptom is that you start out, in this case I had the top down, with the air conditioner running and after the engine warms up (pretty quickly in this heat), the car progressively idles faster at each stoplight until it is up around 2500 RPM. This is hardly an idle any longer. I turned the air conditioner off and it still did it until I had driven it for a while longer.
I tried driving with the air conditioner *off* yesterday and the symptoms disappear.
The question is: what could cause this? I am aware that the engine speed increases when the compressor for the air conditioner kicks in, but it *should* ratchet back down. Is there some sort of sensor that might be kaput?
Michael