Idle Surging Issue

[integratowrx]

Recently noticed that the Saabaru throttle "revs" on its own sometimes.

It specifically happens when the defrost is on and I'm backing out of the driveway or coming to a stop with foot on clutch/brake.  The engine revs to 2k-2.5k rpms.  I know the engine idle typically increases when the defrost/ac compressor runs, but this is higher than normal. 

Car is still under warranty until 26 Jan 09, so I took it to the Saab dealer last week.  They also noticed the issue, but couldn't figure out how to fix it.  They contacted the GM Service Engineers and they determined that it is common with the 9-2X's but not a "problem".  I found a little info about it on nasioc, but nothing too helpful.  I plan to stop by Wagner to see if they've had similar issues with 04-05 imprezas. 

Tubbs, have your parents had any similar issues???

[tubbytreats]

I think the engine "revs" to keep the voltage level in the car up when you have the defrost/AC on and the rear window defrost on and are pushing the brakes (with the headlights on usually)

I'll ask my dad if he has these same issues with their 9-2X but I'm pretty sure they wouldn't even notice.  Do you have the xenon headlamp package?  Heated seats?  Heated Mirrors/Wipers?

I think the use of all of those electronic features is sapping amperage away from the rest of the car and the idle is bumped up a bit higher to compensate.  (It goes away when you release the brake pedal, right?)

[integratowrx]

It actually goes away right when I come to a complete stop, while the brake is still depressed.  I think your assumption is correct about keeping the voltage up, but 2k-2.5k seems a little abnormal to me.  Up until about 5k miles ago, it would kick up maybe a couple hundred rpms when running the defrost/ac (which is what I'm used to with other cars)

I have the base model, so no heated seats, mirrors, or HIDs. 

Also, it seems pretty noticeable (even for a car novice) I think.  I've had multiple people ask me as I come to a stop in their driveway why I'm "revving up the car" 

I honestly don't think it's hurting anything but want to take advantage of my warranty to the fullest extent. 

[tubbytreats]

My car does this frequently now (I'm at 108K miles though) when I have headlights, rear window defrost, A/C defrost, and am braking down a decline. (exit by Dayton Mall off I-75 North is a prime example)

I can watch the voltage meter in my car drop down to 10V or so and the headlights dim until I come to a stop and release the brake pedal.  I'm sure my alternator is weak/going bad or something, but I do notice that the engine will try to rev to counteract the low voltage.

[integratowrx]

How high do the RPMs go when you come to a stop?

I found this thread on Nasioc: http://forums.nasioc.com/forums/showthread.php?t=781242

I think the pics show a wrx engine so I'll have to look around for the IACV on my 2.5 NA

[tubbytreats]

The difference between what I have and what the IACV blockage is has to do with the fact that mine only happens while the brake pedal is depressed and lots of electronics are on (and I can watch my voltmeter drop)  while this IACV issue is a result of just simply idling.