Topic: 2017 STI Idle Issue

[rallyman_03]

So I have my 2017 STI. It has about 15,000km on it and just recently it started developing and idling issue. This issue is only present when the car has warmed up, it throws no codes, and has no drivability issues. It will only do this when stopped at a light or in a parking lot after a drive, etc. Basically what it does, is it will idle normally then blip up to about 1000rpm then drop down to a point where it starts to struggle. Then it jumps back up to about a 1000 then down to normal smooth idle. It will do this every 30-45 seconds. Brought it in to Subaru Calgary and they have told me they cannot replicate the issue, even though I provided them with a video to show them exactly what I was talking about. Video: https://photos.app.goo.gl/1Gto5vYmaaQKDA6C2

Anybody experience this issue, know what could be causing it?

[RockThePylon]

Rad fans kicking on and off?

With the recent cold and Subaru's recent notoriety over ittshay batteries... Maybe it just doesn't have enough ooomph to smooth out the dips, and the alternator is going ham trying to compensate.

[Unholysavage]

May not be the issue, but it could be your AC compressor cutting on/off. Switch your HVAC so that it's on vent, and see if it still idles funny when at operating temps. If you have it set to defrost, the AC compressor will cut on/off every 30 seconds or so and drop idle RPMs when it does.

[Asstuna]

May not be the issue, but it could be your AC compressor cutting on/off. Switch your HVAC so that it's on vent, and see if it still idles funny when at operating temps. If you have it set to defrost, the AC compressor will cut on/off every 30 seconds or so and drop idle RPMs when it does.

^ what he said. It's almost guaranteed to be your AC kicking in. Make sure it's not blowing on your windshield.

[RockThePylon]

Generally the A/C compressor doesn't kick on when ambient temperatures are much below freezing.

[LilDrunkenSmurf]

Generally the A/C compressor doesn't kick on when ambient temperatures are much below freezing.

It will to dry out the windshield on Auto mode.

[RockThePylon]

It will to dry out the windshield on Auto mode.

The light comes on, compressor shouldn't. Somethingsomething head pressure. I'm not an HVAC technician.

It's meant for the sickos on the west coast driving around in 10C rain all winter, not for defrosting your iced up windshield when it's -20.

[Unholysavage]

It only hit freezing temps, what? Monday night? I could be wrong, but it sounds like OP noticed this issue before yesterday.
On my STI the RPMs drop 400 rpm when the compressor cuts in, then surges over 1000rpm. I’m pretty sure I started a thread due to concern as well.

[Rathburn]

Sounds like blown ringlands or something.

[Asstuna]

You're a blown ringland

[silverUURX]

my 13' has done this for basically forever. took it to Subaru and they couldn't replicate it either. let me know if you ever figure something out.

[LilDrunkenSmurf]

I didn't actually read the original post. My 04 STi did this as well. I just never gave a itshay.

[tracker]

I don't know if applies, but I had these exact symptoms in 2 NA cars (2.5RS and Legacy) and it was the beginning of a bad O2 sensor...

[Cagare]

I didn't actually read the original post. My 04 STi did this as well. I just never gave a itshay.

My 09 did it as well.  Did read the original post and my conclusion is, Paranoia.  I suffered it early on in the ownership of my STi, but it went away with time.  Then you modify, and it comes back again, it's a vicious cycle.

If you take a bottle of whisky, open the top, insert the opening in you mouth, and tip the bottle a bit you may start to see this problem go away also.

In all honesty, could be the alternator draw, could be the AC, could be just about anything. If it is really not causing any problems. I would not necessarily worry about it too much.

[05LGT]

I’ve experienced this with many vehicles Subaru or not, seems to be somewhat normal.

[rallyman_03]

It only hit freezing temps, what? Monday night? I could be wrong, but it sounds like OP noticed this issue before yesterday.
On my STI the RPMs drop 400 rpm when the compressor cuts in, then surges over 1000rpm. I’m pretty sure I started a thread due to concern as well.

It sounds like your seeing the same thing as me. This doesn't only happen when its cold. Glad I'm not the only one.

[rallyman_03]

My 09 did it as well.  Did read the original post and my conclusion is, Paranoia.  I suffered it early on in the ownership of my STi, but it went away with time.  Then you modify, and it comes back again, it's a vicious cycle.

If you take a bottle of whisky, open the top, insert the opening in you mouth, and tip the bottle a bit you may start to see this problem go away also.

In all honesty, could be the alternator draw, could be the AC, could be just about anything. If it is really not causing any problems. I would not necessarily worry about it too much.

Okay thanks for the advice. My only questions is can I substitute the whisky for a good single malt?

[rallyman_03]

You're a blown ringland

Oh Asstuna, you know just how to make a guy feel better. Remind me to never ask you if this dress makes me look fat.

[rallyman_03]

It seems like the general consensus is that I shouldn't be too worried. I'll keep an eye on it and if it gets worse I'll harass my dealer. Thanks, everyone. Sorry for the late reply's its been a busy holiday/beginning of the year. (BTW Happy new year!)

[LilDrunkenSmurf]

Okay thanks for the advice. My only questions is can I substitute the whisky for a good single malt?

Absolutely. Bourbon is also acceptable. No rye, however.

[rallyman_03]

No rye, however.

Meh no loss there. lol

[B_Dub]

I have the same issue on my 2018. I find its most pronounced if I've been driving for a while, I don't usually see it on commutes, but it shows up after highway driving or harder driving.