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Idle issue when defrost is on


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I purchased my 05 Legacy (2.5i, yeah I know, terrible) last spring, so this was my first winter with it. I noticed when idling at stop lights or in park the RPM would jump from what I believe is normal range to 1 or just above 1 and then immediately down to where you feel the car is about to stall. It's never actually stalled though. This happened cold or warm.

 

We finally linked it to the defrost, because it only happens when it's on and it does it immediately when you turn it on most times.

 

I took it in and the guy acted like it was no big deal. That when the compressor kicks in it requires a little more juice so the engine revs up. I had something to do that day so I didn't push the issue. But now I want this resolved. I can't believe this would be normal behavior. Is it???

 

I'm taking it back this Friday. Is there anything you guys can recommend I tell this person? He seems to just love to turn people right around and say it's okay.

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Normal... The AC compressor cycles on & off whenever you're using it. When it cycles on, the RPMs go up. When it cycles off, RPMs go down.
"I love the feel of wind in my face and boobies against my back." - BMW motorcycle rider
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Normal... The AC compressor cycles on & off whenever you're using it. When it cycles on, the RPMs go up. When it cycles off, RPMs go down.

 

+1, its just the compressor kicking on and the idle compensator raising rpms for the extra load. Try turning the wheel at a stand still and watch the rpms, should be about the same as the defrost.

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The service manual says the Idle speed when the A/C is on should be @ 800(+/- 100) RPMs, so I think anything above 900RPM may not be normal.

 

It shouldn't feel like it's going to stall at every stop so again that's not normal.

I keed I keeed
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Hey EricP...when you are running around and just need "Defrost" hit the "Mode" button so that the defroster is not running through the AC.....end of problem and remorse.

I found this the second day I had the car...it was annoying until I started shutting off the AC for defrost.

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Hey EricP...when you are running around and just need "Defrost" hit the "Mode" button so that the defroster is not running through the AC.....end of problem and remorse.

I found this the second day I had the car...it was annoying until I started shutting off the AC for defrost.

 

I don't have have a Mode button. If you have the climate control then we're talking about two different systems here. I have the base version.

 

To test your theory I just took it for a spin and ran the defrost with the AC, no change. Turned off the AC, no change. If the defrost is on in any shape or form, the RPMs will jump periodically at idle.

 

For the record, it jumps enough to actually move the car while my foot is on the brake. Maybe just an inch or two, but enough to make me think my car has a mind of its own and wants to take off when it wants to take off. If everybody here can say their Legacy does this, then I'll deal with it. But I really don't think that's the case. I guess I know why it does it. I just want to know if it's normal. If it's not, then it needs to be fixed.

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I don't have have a Mode button. If you have the climate control then we're talking about two different systems here. I have the base version.

 

To test your theory I just took it for a spin and ran the defrost with the AC, no change. Turned off the AC, no change. If the defrost is on in any shape or form, the RPMs will jump periodically at idle.

 

For the record, it jumps enough to actually move the car while my foot is on the brake. Maybe just an inch or two, but enough to make me think my car has a mind of its own and wants to take off when it wants to take off. If everybody here can say their Legacy does this, then I'll deal with it. But I really don't think that's the case. I guess I know why it does it. I just want to know if it's normal. If it's not, then it needs to be fixed.

 

It definatly does not sound normal, take it to the dealer and have it fixed under warranty.

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When running the Stop Light Gran Prix always turn off A/C for more get away power. Just pretend your hitting the Nawass(NOS) button. Zooooom!

 

Edit: I think the LGT shuts off the compressor @ WOT?.?

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When running the Stop Light Gran Prix always turn off A/C for more get away power. Just pretend your hitting the Nawass(NOS) button. Zooooom!

 

Edit: I think the LGT shuts off the compressor @ WOT?.?

 

It does

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Subies add even a little more RPM when the engine is still cold. I swear I saw a jump to over 2K on the tach on a cold start, foot off the gas. Drove a bit.. idle.. jump again.. drove away.. when the engine warmed up.. finally normal idle revs.
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Anyone else experience this? When I drive away on a cold engine, there is a definite stutter as it goes past 2200 RPM...nothing to do with defrosters but it is very noticeable in cold weather until the engine is at normal Op temp.
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So I get to deal with a car that feels like it's going to stall at every stop? Wow, where's that thread about buyer remorse?

No, you need to find a dealer that will adjust the idle setting to normal specifications. This can be done without drama at most dealerships.

 

What dealership did you take it to and who did you speak with? Adjusting the idle up a little will solve the problem. That "1" refers to 1,000 rpms and the idle is probably around 600-700. Tell the service writer it's a safety problem, and as long as he is willing to put in writing to you that this is "normal" you'll live with it. It could become a safety problem if your engine stalled.

 

Often, breaking in the engine will also solve the problem, how many miles do you have on your car?

 

If you are feeling an inferiority complex for having the legendary 2.5l Subaru flat four that accounts for 60-80% of their sales, post on ultimatesubaru.net, a much more maintenance-oriented forum than this one.

Who Dares Wins

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Eric, wait till you get to Seattle and have Carter Subaru look at it. They are one of the best. Subaru service on the west coast is much better than the midwest in general.

 

For a minute I thought you knew me, then I looked at my location.

 

I hope you're right about the service out west. Every other car in Seattle is an Outback :icon_lol: , so they have more experience, that's for sure.

 

I dropped it off last Thursday and heard from them yesterday. Same thing. They say it's normal. I say if every car on the lot does this, I'll be amazed. And I'll never even think about buying another Subaru. Actually, when I pick it up I'm going to drive a few and see. If none of them do it, Team Subaru of Michiana is going to see a lot more of me.

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