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bhlerman 12-06-2012 12:47 PM

Rough idle with AC on
I just had the timing belt and water pump replaced and plugs replaced along with some other repairs on my 1996 legacy outback 2.5l DOHC. Now the car idles rough when the AC is on (no problem before the repairs). Otherwise runs fine. The mechanic says the AC compressor may be going bad. I think it may have something to do with the timing belt. Any help?

monkeyposeur 12-07-2012 12:21 AM

My compressor is kind of messed up ever since I decided to be a dumbass and charge it with a can of refridgerant from the parts store. But it doesn't really affect my idle.

You say it runs fine otherwise. Does this mean that the idle is just fine when the AC is off, and when you turn the AC on it idles rough?

edit: Oops, you specify that it runs rough only when the AC is on. Maybe I shouldn't post after working double shifts.

Tr00b 12-07-2012 06:26 AM

Clean your iac it may not have enough airflow to compensate for the added demand of the compressor running.

bhlerman 12-07-2012 01:24 PM

After more checking I think it is the engine mounts. The idle is more of a vibration than rough. It happens only when the AC is on and the car is stopped and in drive or reverse. I would think if it is a problem with the timing belt adjustment the car would be running worse or not running.

G Man 12-07-2012 05:07 PM

I have to agree with the mecanic. probily a lack of oil in the pump.

bhlerman 12-17-2012 12:49 PM

The vibration is getting worse. Now it happens also when the AC is off (but is worse when AC is on). It happens when stopped and in gear with the brake on. When I had the work done on the car I also had both front axles replaced because the boots were bad. I have been reading on the internet that replacing the axles with rebuilt non Subaru axles can cause this. Doesn't make sense but it seems to be a reported problem after replacing the axles. I'm taking the car back to have it checked for motor mount problem. If that is not the problem then it is probably the axles. I don't want to spend the money again replacing the axles with expensive Subaru axles. Would it be a problem to not replace the axles and live with the vibrations?

Stang70Fastback 12-17-2012 04:38 PM

I've had the axle vibration issue for... many years now... and nothing has blown up yet, so I think you're fine.

I was speaking to a friend mechanic who told me that this "axle nonsense" can actually be fixed by adjusting the wishbone... or dogbone... I think he said it was at the rear of the engine near the tranny. Does anyone know what he was referring to?

SubN00b 11-09-2014 10:16 AM

Explanation requested: axle-based vibration relation to electrival system
I know this is an old topic (on many forums), but I am still confused by the connection between the axles and the symptoms.
1) I sort of understand how having "bad" axles could cause a vibration while in drive, even if you're not moving.
2) I DO NOT understand how the AC could exacerbate the vibration.
3) After replacing my spark plugs the vibration went away for a couple weeks, but then it came back - how would new plugs affect the vibration?

I am feeling like I'm either missing something in how the car's electrical energy affects its mechanical energy or my problem is not confined to the cheap axles.

I would really, really appreciate a response from someone that understands this problem well.

johnegg 11-09-2014 12:31 PM

1/ cheap axles do not cause the vibrations.
they simply transmit the normal engine vibrations to the wheels and chassis of the car.
this has to do with the low quality of the axle.
high quality axles do not transmit these vibrations.

2/ if you feel the vibrations more when the AC is on,
then the engine vibrations are greater when the AC is on.

3/ if you felt the vibrations less with new plugs,
then i have to assume there were less vibrations with new plugs.
and therefore if the vibrations increased after a few weeks, so did the normal engine vibrations.

i'm not at all sure this is what is actually happening on your car.
but this is how cheap axles cause the car to vibrate, especially at stop lights in D.

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