jumpy idle speed... is this normal?

[volkl23]

Hi everyone! I've put around 400 miles on my Sti and I've noticed something that seems a bit odd.

When I'm at a long stoplight, my idle would sometimes go up and down. For example... normally it's around 4-5k, but sometimes it would go really low like it's about to stall, and then all of a sudden the idle would jump a litle bit to 5-6k (i guess to prevent it from stalling). I thought this might have been due to the compressor turning on and off, but I've noticed this with the ac off.

Is this normal and has anyone experienced this as well?

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[Zoso]

My car does the same thing.

[wrxtuner02]

i hope you don't mean 4-5000 rpm. that is a little high.

look at your guage again. the first mark on the taco is 500 rpm then 750.

yes it is normal to flucuate slightly especially when the ac compressor is on and when the fans kick on and off.

[wewu]

a little ot here but ne one get this when they cold start their car. The car idles at 2k then slowly as it warms up drops to normal 500rpm?? Then one time during a cold start the car was at 2k idle then as I pressed the clutch to reverse out of my driveway the rpm started to rev. Scared me so I let out the clutch and the idle returned to 2k. Seemed that the clutch was acting like the throttle for a second there, ne one know what that was??

[RichQY]

idles @ 4-5K.


omg...

must be an anti lag system..



mine idles at around 6-700, doesn't fluactuate that much, only visible differnece is when the fan turns on and off

[volkl23]

Sorry guys! I meant that the tach is around 400-600, but it would drop a little and then surge to 500-600 over and over again. I would say the cycle is around a min or so. The compressor is off when this happens.

Weirdness.

[Kostamojen]

Every subaru ive been in does that.

[QUICKONE]

Originally posted by volkl23
Hi everyone! I've put around 400 miles on my Sti and I've noticed something that seems a bit odd.

When I'm at a long stoplight, my idle would sometimes go up and down. For example... normally it's around 4-5k, but sometimes it would go really low like it's about to stall, and then all of a sudden the idle would jump a litle bit to 5-6k (i guess to prevent it from stalling). I thought this might have been due to the compressor turning on and off, but I've noticed this with the ac off.

Is this normal and has anyone experienced this as well?

Mine did this when I had the malfunction in the A/F sensor and the surging problem while driving.(see thread "car feels like it's surging) Since they fixed this problem idle is very smooth no noticable flucuations. Have them check the A/F sensor.

[PRGWRX]

mine has done that for a while<idle at 600...sometimes it even sounds like its about to cut off or give a rotary sound when just turning on the car. always wondered if that was a problem or not


frederick

[Janq]

My STi has been doing the same but only recently (last 800 miles or so). When I take it in for a 2K mile fluid change and general check over I'll inquire about it.

It sounds & feels similar to old muscle car engines with big loping cams at idle. Also I noticed that my headlights some times dim for a split second at idle. My '04 Honda Pilot w/VTEC is well known to do the same thing and its a normal condition. As such I figured the weird idle might have somthing to do with the AVCS system.
I too at times have thought the engine was going to cut out. It seems to do this only when the engine is warm and been under load for long stretches (i.e. highway) and then brought down to stop & go traffic conditions. I've not noticed the effect on a cold engine or when commuting only.

This is my fifth Subaru owned and second in my current possesion. I've never noticed this phenomenon on any other model.

- Janq

[volkl23]

Originally posted by Janq
My STi has been doing the same but only recently (last 800 miles or so). When I take it in for a 2K mile fluid change and general check over I'll inquire about it.

It sounds & feels similar to old muscle car engines with big loping cams at idle. Also I noticed that my headlights some times dim for a split second at idle. My '04 Honda Pilot w/VTEC is well known to do the same thing and its a normal condition. As such I figured the weird idle might have somthing to do with the AVCS system.
I too at times have thought the engine was going to cut out. It seems to do this only when the engine is warm and been under load for long stretches (i.e. highway) and then brought down to stop & go traffic conditions. I've not noticed the effect on a cold engine or when commuting only.

This is my fifth Subaru owned and second in my current possesion. I've never noticed this phenomenon on any other model.

- Janq

My Sti is doing the same thing after long drives and I stop. I never see this at cold starts other than my idle going pretty high (to warm the engine). My car has only 400 miles on this and it's doing this, as opposed to your's Janq at 800. Is this something worth taking in to inquire about at the dealer?

[Janq]

Originally posted by volkl23


My Sti is doing the same thing after long drives and I stop. I never see this at cold starts other than my idle going pretty high (to warm the engine). My car has only 400 miles on this and it's doing this, as opposed to your's Janq at 800. Is this something worth taking in to inquire about at the dealer?

I'm just over 2K miles as of last night and I first noticed the idle lumpiness at about the 1200 mile mark.

Now that other folks are reporting the same thing I'm begining to think this just might in fact be a normal condition for STi's. I'll still ask about it though when I go see my Subie master tech.

It doesn't bother me though as its just caught me by surprise when it first started to occur. Again, the Honda Pilot does exactly the same thing and mine in specific has been since I drove it off the dealers lot.

One other item, this idle lumpinesss seems to occur most often when the A/C is off. I tend not to use A/C in my cars at all (I just don't like it and prefer an open window) but I find that under similar/same conditions with the A/C activated I do not get the idle lumpiness. Just an observation...

Thus far the only item that truly bothers me about this car is the notchiness of my shifter mechanism. At times it's resistant to shifting in/out of gear without a bit more authority than I'm used to (probably a remnant of its race application). Also the internal shift gate could have been a bit more precise as it takes a lot of getting used to.

- Janq

[renichms]

Originally posted by wewu
a little ot here but ne one get this when they cold start their car. The car idles at 2k then slowly as it warms up drops to normal 500rpm?? Then one time during a cold start the car was at 2k idle then as I pressed the clutch to reverse out of my driveway the rpm started to rev. Scared me so I let out the clutch and the idle returned to 2k. Seemed that the clutch was acting like the throttle for a second there, ne one know what that was??

With a cold start, mine idles at 1500 RPM until it warms up or until I start moving (which makes it not idle, obviously...).

RN

[happasaiyan]

i get the boxer "shake" in mine, but only once have i experienced the symptom you guys describe. kinda scared me, and luckily never came back. i had a similar problem in my celica before, and all i had to do was make sure the intake tubing was properly secured. the maf gets messed up if there is a leak.

[old blue]

I was wondering if the erratic idle had something to do with
the on board diagnostics...