Strange revolutions

[Avid Edit]

Greetings all,
While cruising along at about 60MPh,
the revs floated from about 2k to 2500,
no speed change, no shifting, just the visual
and audible from the engine, as if revving in
neutral...AC on.
Any thoughts..???

[barrysharp]

Curious to know what the period was going from 2K to 2.5K rpms. For example, was it 2 secs or more like 30 secs ?

There was another posting of a similar nature by a forum member in Mexico and Jason responded to it by saying it was or could be caused by auxillary equipment going from idle to active such as the A/C unit.

It is strange that no speed change occured.

[Avid Edit]

Barry,
Maybe 3-8 seconds in duration,usually one would feel a "tug"
when the compressor kicked in,yes?

[barrysharp]

Sometimes yes and sometimes no. The A/C compressor in modern cars is very stealthy. http://xc70.com/iB_html/non-cgi/emoticons/wink.gif

Were you in CRUISE mode ? Was road straight and level ? What about a variable strong head/tail wind ? Were any large trucks passing you by going in either direction ? Was a large truck on your tail somewhat ?

[Avid Edit]

Barry,
      Straight and level..??? I live in NYC. http://xc70.com/iB_html/non-cgi/emoticons/biggrin.gif
       actually, very little traffic, no cruise , no trucks,
       just the usual gang of idiots on the road. I hope this
       will remain  in  the fluke category. Oh by the way, I do  
       have have one of those split-view side view mirrors,
       came in handy..check Borton Volvo.

[emil]

It seems that higher power demand caused by some equipment such as A/C kicking in is a good explanation.  I have noticed revs going up and down at neutral by about 1k rpm once on my car.  Apparently throtle/fuel injection system required cleaning (the car has over 100k km done). Have not happened afterwards.

[Hiro's XC]

It sounds like the transmissions torque converter unlocked or a few seconds. This will cause the RPM increase in the range you mentioned. The reason why? Who knows. Some electrical glitch, a quick minute bump of the throttle caused it to shift, really hard to say. A load change from the A/C wouldn't cause that big of a bump though. As long as you didn't get a check engine light just have the dealer check for a fault code at the next service.

Jason