Hot weather fast idle

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

> 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.
>

My '97 was doing that, although not to 2500 RPM. More like 1200rpm. I
cleaned the throttle body and idle air control valve with carb cleaner
spray and the problem went away. I'm pretty sure the 2003 model is
different with regard to idle control than my 97, but if you can
locate the IAC I would suspect it is stuck and/or sticking due to
carbon buildup. Cleaning it might put you back in business.

Good luck with it...

Chris

On Jul 9, 11:50*am, Hal > wrote:
> > 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.
>
> My '97 was doing that, although not to 2500 RPM. More like 1200rpm. I
> cleaned the throttle body and idle air control valve with carb cleaner
> spray and the problem went away. I'm pretty sure the 2003 model is
> different with regard to idle control than my 97, but if you can
> locate the IAC I would suspect it is stuck and/or sticking due to
> carbon buildup. Cleaning it might put you back in business.
>
> Good luck with it...
>
> Chris

Thanks!