Originally Posted by Red Baron
for some reason when i turn on my heat or a/c and i stop the rpms go up to about 1200 then back down to 900 and it keeps doing this until i start driving. does anybody else have this problem or does anyone have a fix for this??? any help would be awesome cause the warm weather is coming and i dont wanna sound like im trying "show off" everytime im stopped a light with the a/c on.
Sounds like it'* boosting the idle speed to compensate for the A/C compressor coming on, but then the compressor cuts out again, so the idle whooshes up momentarily. If the compressor itself is cycling on and off (e.g. low Freon), that could make the idle speed wander up and down as the compensation kicks in and out.
Can you lift the hood and watch what'* going on when this occurs?