Before I take it in and have the dealer guess on what the issue is I
thought I'd post and see if anyone has past knowledge of this issue.
2008 Aveo5 AT, 5k miles. When I coast with my foot off the throttle I
get a regular pulsing drop in RPM's. Normally from 50mph to around
35mph as the car slows the rpm will drop from 1600 to 900 or so and
then back up 1600. I first I thought it was downshifting as the car
slowed by I know I don't have 10 gears. It feels like someone is
touching the brake every second or two. I have tried this coasting
in neutral and of course I don't feel the slow down like when in gear
but I do the the rpm gauge bouncing up and down.
I have not have any codes or warning lights. I do have a scangauge
attached.
Any ideas ?
Steven

 

Downshifting will cause RPMs to increase, but cause the car to slow. [/align]You might have to get the codes read at an auto parts store to get a better diagnosis but I don't think that its downshifting.[/align]

 

Are the HVAC controls off? If they are on, is it set to defrost or is the a\c on?
Could be the compressor coming on and off

 

HAVC controls off, even tried with the fan completely off and it still does it when my foot is off the gas and coasting. If I turn on the air it seems to hold a little more throttle than normal and actually doesn't see do do the rpm drop. If I put it in Neutral when coasting off the freeway of course I don't feel it like when it's in gear but I still can see the rpm's just bouncing up and down.