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Old 05-11-2006, 11:06 AM   #1
ArtechnikA
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Default occasional high idle (warm) EJ25D

'97 Legacy Outback Limited. Occasionally (1X in maybe 30-50 starts) the engine idles high (1400-1600 rpm) and will not back down to ~800 like it does normally.

switch off and restart always (so far!) restores correct idle - so I have to think something is confusing the ECU. ideas on what?

my WAG was some kinda coolant temp sensor.

I *have* unplugged/replugged the connector to the idle control valve, verified that it is not corroded or gunky, to no (noticeable) effect. (no stored DTC's to guide me...)

thanks in advance...

---rich
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Old 06-28-2006, 11:19 AM   #2
ArtechnikA
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Problem is still there, and seems to be getting worse. Read the other 'high idle' threads but found no inspiration there.

So let me ask: *what* (exactly) brings back the idle when the engine is warm. I'm expecting to see a chain like [some sensor] -> ECU -> IAC. I just don't know what or where [some sensor] is.

happened last night, and this morning. engine fully warm, 1800rpm idle in neutral. kill the ignition, restart, perfect 800 rpm.

Could it just be a sticky IAC? the one in the car now is the "known good" one. would switching off the ignition reliably "unstick" an IAC?

still no DTC's - i have learned not to let it idle high in neutral for too long lest it kick out the 'uncontrollable idle' DTC and switch off the #1 injector (BTDT). so far - keeping in in D drops the idle enough to prevent that symptom even when it's screwing up, but that's not acceptable from a brake wear or fuel mileage standpoint...

so I ask again - for all you Subie-trained techs out there - What sensor(s) does the ECU read to determine "warm engine" and where are they? ('97 EJ25D for those who've not been following along...)
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Old 06-28-2006, 07:29 PM   #3
MonsterRallySport
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Do you have an oiled air filter?
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Old 06-29-2006, 02:26 PM   #4
ArtechnikA
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Quote:
Originally Posted by MonsterRallySport
Do you have an oiled air filter?
As a matter of fact, I do.
But I had the problem first :-) ...

I was assured by some with good reputations here that the K&N wouldn't present a problem with the MAF - something I've learned is a chronic issue with Porsche 986/996 and many VW's.

Are you suggesting this can be a fouled MAF issue? I can clean it and give it a try if you think it'd help. My fuel economy has been sucky but I attributed that to the ethanol; the car has been performing well otherwise without the driveability issues that seem to accompany bad MAF problems in other cars...
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Old 08-15-2006, 09:31 PM   #5
Imprez04
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meh although i have a different high idle problem....

i had this one first.



do you have cruise control? my car was doing the same exact thing, i finally brought it to a dealership (i was out of warrentee so i was reluctant to go) and they found it was a bad cruise control belt.

it could be a different thing though, seeing how my car now likes to idle at 2500-5000 on occation now...


but hell, you might want to just check that out
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Old 08-15-2006, 10:00 PM   #6
ArtechnikA
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Quote:
Originally Posted by Imprez04
do you have cruise control? my car was doing the same exact thing... it was a bad cruise control belt.
but hell, you might want to just check that out
cruise control belt?

no belt I know of in a '97...

I have checked the cable - no preload. it happens whether I have the CC on or off. I can be driving (coasting...) along in neutral, 1800 rpm, turn off the engine, immediately turn it back on - bingo - solid 800 rpm idle, and it'll be like that the rest of the drive. this never happens when restarting hot - only from a "cold" (sitting all day...) start.

I'm thinking maybe it's a temp sensor that never notices the car has warmed up, needs a reboot to smack it.

one thing I haven't yet had the opportunity to check is the throttle % open when it's screwing up. PITA to drag the laptop around plugged into the OBD-II port logging it all the time on the off-chance i'll catch it...

but keep those ideas coming - it's gotta be something...
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Old 08-16-2006, 12:33 AM   #7
Storm
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Might try cleaning the IAC valve.....It could be getting a little gunked up.

Jay
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Old 08-16-2006, 05:34 AM   #8
ArtechnikA
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Quote:
Originally Posted by Storm
Might try cleaning the IAC valve.....It could be getting a little gunked up.
I did clean the IAC really well when I installed it on this engine, which had a way too-high idle when I first put it in - I moved over the IAC from the original, trouble-free (except for those head gaskets...) engine and it was still too high, (tripping the 'uncontrollable idle' DTC) but it did adjust down.

What's the recommended/preferred way of cleaning an IAC? If there's a "right" way I'll definitely do it. (I have, as you may have read in this thread, verified that the electrical connection to the IAC appears sound.)

Is it plausible that cycling power to the IAC would make it unstick? I may just try pulling the connector and replacing it to cycle only that component, if I can catch it screwing up under relatively convenient circumstances for this...
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