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Old 09-07-2006, 02:16 PM   #1
Slalom RS
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2004 TS Wagon

Default Surging/pulsing idle with AC on?

I did a search, but the silly two-letter rule prohibits any topics with 'ac' in it.

Car is a 2004 TS Wagon with about 35xxx miles on it. I've had it for about a month now. I'm noticing a pretty annoying idle pulsing when the AC is on. Note that this ONLY happens when the AC is on. At normal idle, it sits somewhere between 600 and 800. Every 10 seconds or so, it will surge up to 1800-2000 for a few seconds, then come back down. With a Prodrive exhaust, the pulsing is quite noticeable, even from outside the car. Inside, it drives me nuts at stoplights and such.

Is this normal? What can I do? Factory warranty runs out really soon, should I take it it?

Thanks.
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Old 09-07-2006, 07:50 PM   #2
Hayes
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My 2000 Forester idles at ~750 and when the AC compressor kicks on the idle increases to ~ 900 rpm. Something is wrong with your car so take it in.
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Old 09-07-2006, 08:07 PM   #3
Master2192
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First, its usually called A/C, searching for that probably would have had some results.

I would take it in if it is still in warranty. alittle bit of surging (say 100 rpms) from the compressor kicking on would be normal. jumping to almost 2k would leave me to believe you've got a clogged Idle Control Valve. You could try cleaning it yourself and see if that fixes the problem, or have subaru do all the work for free.
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Old 09-08-2006, 05:25 PM   #4
BURTONRIDR
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Prodrive exhaust? Have you checked to make sure you dont have an exhaust leak somewhere before the O2 sensor? I dont know which parts are part of the prodive exhaust..... But I just put borla headers on and my exhaust is leaking and my idle is irradic with the A/C on.
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Old 09-08-2006, 08:54 PM   #5
rebbeach611
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just check igition coil,,,,plug wire...spark plug...

i got same problem..my old Audi A4...

Dealer changed A/C compressor...check o2 sensor..etc etc...but still not fix up.

Finally. i brought it to small garage....it turns out bad ignition coil....i spend few hundreds dollar for wrong diagnosis......i could not get money back from dealer......

just find well experienced mechanic...you can save bunch of money..
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Old 09-10-2006, 09:47 PM   #6
Slalom RS
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Quote:
Originally Posted by BURTONRIDR View Post
Prodrive exhaust? Have you checked to make sure you dont have an exhaust leak somewhere before the O2 sensor? I dont know which parts are part of the prodive exhaust..... But I just put borla headers on and my exhaust is leaking and my idle is irradic with the A/C on.
Which O2 sensor? I know there's one down before the cat. Probably wouldn't hurt to tighten the header bolts before that. Is there another one? I come from Hondas, and those O2s are right on the exhaust mani at the front.
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Old 09-11-2006, 10:31 AM   #7
BURTONRIDR
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Quote:
Originally Posted by Slalom RS View Post
Which O2 sensor? I know there's one down before the cat. Probably wouldn't hurt to tighten the header bolts before that. Is there another one? I come from Hondas, and those O2s are right on the exhaust mani at the front.
There are two o2 sensors, one is before the cat, and the other is right after the cat. I would turn your car on and just looke under the car to see if exhaust is coming out around where the header (if you replaced it or took it off while changing exhaust) and then also look at the connection between the header and the cat.

Last edited by BURTONRIDR; 09-11-2006 at 10:38 AM.
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Old 09-11-2006, 12:12 PM   #8
Slalom RS
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Quote:
Originally Posted by BURTONRIDR View Post
There are two o2 sensors, one is before the cat, and the other is right after the cat. I would turn your car on and just looke under the car to see if exhaust is coming out around where the header (if you replaced it or took it off while changing exhaust) and then also look at the connection between the header and the cat.
I just bought the car, and the original owner did install new headers. I was under there doing an oil change the other day and didn't notice any obvious air leaks, but it might not hurt to get under there and tighten everything. Thanks.
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Old 09-11-2006, 01:57 PM   #9
BURTONRIDR
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Yea it wouldnt hurt to double check everything.... I just know that my car gets very cranky when it doesnt know how much fuel to mix with the air
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