Skip to content
View in the app

A better way to browse. Learn more.

Ultimate Subaru Message Board

A full-screen app on your home screen with push notifications, badges and more.

To install this app on iOS and iPadOS
  1. Tap the Share icon in Safari
  2. Scroll the menu and tap Add to Home Screen.
  3. Tap Add in the top-right corner.
To install this app on Android
  1. Tap the 3-dot menu (⋮) in the top-right corner of the browser.
  2. Tap Add to Home screen or Install app.
  3. Confirm by tapping Install.

What Controls Idle RPM?

Featured Replies

I LOVE my "new" '97 Outback Limited. Great car. It's got just shy of 100k miles on it and is going strong. One question though...

 

What controls the idling rpm? I've noticed that sometimes it'll idle at 1500 and sometimes at 800. Why would this change? My old car did this too.

 

Thanks,

Reid

The Idle is controled by the ECU. The ECU will very the idle speed based on engine temp and load. When the engine is warm 800 rpm is about right and when the engine is cold 1500 is about right. Also if the AC or Defroster is on, the engine will idle faster to compensate for the added load of the AC compressor.

GLCraigGT: That little blue fella to the left of your name?

 

Is that what a head-gasket leak looks like?

GLCraigGT: That little blue fella to the left of your name?

 

Is that what a head-gasket leak looks like?

 

No, that is what a Subaru Owner looks like when his (or her) headgasket blows, and they see the bill. . .

 

I also have a question about idle speed. On my '92, it tends to "hunt" a bit. Is this a clear indication of some condition or other (O2 sensor going? TPS? Something else?)?

No, that is what a Subaru Owner looks like when his (or her) headgasket blows, and they see the bill. . .

 

I also have a question about idle speed. On my '92, it tends to "hunt" a bit. Is this a clear indication of some condition or other (O2 sensor going? TPS? Something else?)?

 

The hunting is usually either a vacuum leak (check all the hoses around the throttle body or perhaps the MAF air flow unit

  • 5 years later...

what about cleaning the idle air control valve (IAC)? That seems to remedy some of these high rpm problems.

what about cleaning the idle air control valve (IAC)? That seems to remedy some of these high rpm problems.

 

I agree that it is also very likely a vac leak or bad ECU temp sensor (on the coolant pipe that runs over the bock and under the intake manifold, passenger side).

my 97 Legacy OBW had a terrible erratic idle about 2 months ago. i checked every hose on that thing. no vacuum leaks. i removed and cleaned the iacv and that fixed it. btw, if you do clean the iacv make sure to replace the gasket with a new one. curtis

Please sign in to comment

You will be able to leave a comment after signing in

Sign In Now

Account

Navigation

Search

Search

Configure browser push notifications

Chrome (Android)
  1. Tap the lock icon next to the address bar.
  2. Tap Permissions → Notifications.
  3. Adjust your preference.
Chrome (Desktop)
  1. Click the padlock icon in the address bar.
  2. Select Site settings.
  3. Find Notifications and adjust your preference.