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Old 06-30-2007, 12:07 AM   #1
zzzzzzzz
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Unhappy Need help...rough idle...acceleration stumbling.....

I have an 01 Legacy and have been having this issue for the last year now. Starting up, the car runs fine; very smooth idle. If I go close to WOT or push the car in anyway or go uphill, my acceleration will start to stumble. Then from that point forward when I let go of the throttle and press again, my engine stumbles. Also, when on this same trip and I get to idle, the engine will sound like it revs down and then up and then down and the up and then down, with the RPM gauge not moving. About 5-6 times up and down and the car goes back to normal idle. With the A/C and in Neutral the car still stumbles, no difference. Also, if I were to turn the engine off and on again, the car is back to normal.

So, no mods on the car. And this is what I've done thus far:

-replace fuel filter
-checked all vacuum lines to and from cruise control, intake
-replaced spark plug wires, plugs, gaskets around plugs, valve cover gasket, etc.
-replaced alternator
-replace air filter
-replaced timing belt

My cruise control doesn't work though the light comes on, but I think it's because I purposely disconnected two of the four tailights.

What do you guys think?
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Last edited by zzzzzzzz; 06-30-2007 at 12:14 AM.
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Old 06-30-2007, 02:04 AM   #2
MkIII
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I had a similar problem based on your description. Although I'm definitely no expert on this, so consider it with that in mind.

In my case, I went the route of nearly replacing every ignition related component until I finally threw in the towel and took the car to the dealership. Turned out that it was the Air/Fuel Ratio Sensor that had gone sideways. After that was replaced, the car runs really well.

Here's my thread: http://forums.nasioc.com/forums/show....php?t=1290270
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Old 06-30-2007, 09:25 AM   #3
zzzzzzzz
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That's the thing though, it never has thrown a CEL at all this past year. And the stumbling problem comes and goes. Is yours like this as well? Does it stumble and buck all the time or only when you push the car? Is there a way to check the AF sensor? Where did you take it in?
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Old 06-30-2007, 11:13 AM   #4
MkIII
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Mine would come and go for a while. Some days I'd head out and I'd feel hesitation right away, others it wouldn't do a thing. There was a definite loss of power, but I didn't realize that until it was repaired.

It behaved like this for quite a while and didn't throwing CEL's until about 2-3 weeks ago. Then, as I mentioned in the other thread, the code suggested a completely different course of action. Although in retrospect it seems clear that had I known more about the motor I might have added the A/F Ratio sensor to the suspect list.

I'm not sure of a way to check this sensor outside of a service department. If there is a way, I'd sure like to hear myself and save some money in the future. I usually take my car to Royal Moore in Hillsboro for things like this. Previously, I took it to Wentworth in Downtown Portland. I don't have any complaints about either place so far.
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Old 06-30-2007, 04:14 PM   #5
zzzzzzzz
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I think my course of action is to go into autozone, get a code, if one similiar to yours come up, i'll go into a dealership for a diagnostic. How long was yours hesitating before the CEL came up?

One thing on mine is I continually disconnect my battery to reset, which may have not allowed the ecm to learn a problem.
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Old 07-17-2007, 10:39 PM   #6
zzzzzzzz
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So I just went into Autozone, and on my way there the car was stumbling bad. At each stop, after stepping on the gas there was a good amount of hesitation. Get to Autozone finally, with a sign of relief because the car seemed like it wanted to turn off the entire way there. They checked for codes and NONE returned.

Need help, because this is just killing me.
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Old 07-17-2007, 10:55 PM   #7
FLAT4motorsports
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check your idle control valve.....thats probably whats creating your problem....
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Old 07-18-2007, 08:22 PM   #8
zzzzzzzz
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If ordered, it's a +$300 dollar part. And is it this part (22650)?:



I've seen how we can clean the "other version" IAC with the coolant tubing going in and new gasket, and I've checked this part, there was what looked like a lot of carbon build. I've cleaned it and no improvement. Any suggestions? Do I even have the right part? Thanks.
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Old 07-18-2007, 09:11 PM   #9
lgt2000
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off topic but what program are you using there?
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Old 07-18-2007, 10:33 PM   #10
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Quote:
Originally Posted by lgt2000 View Post
off topic but what program are you using there?
Looks like a screen capture from the dealership parts system?
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Old 07-18-2007, 10:40 PM   #11
zzzzzzzz
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Yeap, dealership. Just trying to find out exactly where the IAC is on this car. Any suggestions, anybody?

Actually, what the correct way to clean the IAC on these models?
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Old 07-18-2007, 11:42 PM   #12
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Assuming we're referring to the idle air control solenoid, PM me with an your email for the FSM page (I can't host non-image files, and the doc is PDF).

In any event, techninfo.subaru.com has the FSM online (non-indexed PDF's - GRRR).
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Old 07-18-2007, 11:59 PM   #13
zzzzzzzz
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Quote:
Originally Posted by sadsack View Post
Assuming we're referring to the idle air control solenoid, PM me with an your email for the FSM page (I can't host non-image files, and the doc is PDF).

In any event, techninfo.subaru.com has the FSM online (non-indexed PDF's - GRRR).
Sent you a PM! TIA Matt
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Old 07-19-2007, 02:00 PM   #14
zzzzzzzz
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So last night I removed the IAC "solenoid" (thanks sadsack) and the solenoid itself was clean, as I had cleaned this earlier, couple months back. But what I did in addition that I didn't do was clean the chamber the solenoid slides into, on the TB. Again, covered with carbon deposits like nobody's business. Used a cloth and qtips soaked in IPA. Drove the car this morning on my usual commute, everything is ok, no surging, sputtering, car acting like it's dying. Though one thing the commute this morning was pretty brisk, not a whole lot of normal stop and go. I'll drive the car a few days and see if the problem occurs (cross my fingers, hope this doesn't get jinxed).

We'll see...
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Old 07-20-2007, 12:33 AM   #15
MkIII
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I know I sort of dropped off the face of the earth (had to get married, honeymoon, that old story). Anyway if it helps any, provided you didn't fix it by what you've done already, they told me that my car actually ran better in limp mode when they disconnected my A/F ratio sensor, than it did when hooked up.

That was what tipped them off to this as the cause initially. So you might try that as an option. The day I finally took it to the dealership my car barely made it.
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Old 07-20-2007, 02:22 PM   #16
zzzzzzzz
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Quote:
Originally Posted by MkIII View Post
I know I sort of dropped off the face of the earth (had to get married, honeymoon, that old story). Anyway if it helps any, provided you didn't fix it by what you've done already, they told me that my car actually ran better in limp mode when they disconnected my A/F ratio sensor, than it did when hooked up.

That was what tipped them off to this as the cause initially. So you might try that as an option. The day I finally took it to the dealership my car barely made it.
Augh, either i don't treat this car well or it just hates me. I still have the hesitation issues, but it's not as pronounced as before for whatever that's worth. I'll try to disconnect the af sensor tonight and see if the car runs better, if not the same.
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Old 07-23-2007, 02:31 AM   #17
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You have a blown MAF sensor!!! get it replaced or even just clean it. (maybe its not blown) just very dirty with dirt/dust etc...
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Old 07-24-2007, 11:29 AM   #18
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as MkIII mentioned, I would check the Air/Fuel ration sensor. I had similar issues on my 00 Legacy and an 01 Forester. Neither threw a CEL but both were fixed by replacing the A/F sensor.
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Old 07-24-2007, 07:41 PM   #19
zzzzzzzz
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Okay, I'm just going to pick up an a/f sensor for the heck of it tonight on my way home. At their costs, I'll get it for $97 and some change. The nice thing is the sales rep there said they'll take it back from me even if it doesn't work, which she says they typically don't but since 1) i've been going there often enough she'll allow it, and 2) they have quite a few on the shelf, so taking one back she says is manageable.

One thing I question right off is, "why would they have a lot in stock?" Is this a part that is replaced often enough?

Wish me luck!
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Old 07-24-2007, 07:44 PM   #20
zzzzzzzz
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Quote:
Originally Posted by sweezeyd View Post
You have a blown MAF sensor!!! get it replaced or even just clean it. (maybe its not blown) just very dirty with dirt/dust etc...
I think the legacies have an MAP? I might be wrong....
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Old 07-24-2007, 07:49 PM   #21
zzzzzzzz
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Here's a picture of where the a/f sensor is, if anyone is wondering:

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Old 07-29-2007, 01:20 PM   #22
MkIII
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Actually, I was and now I know there was at least some effort involved in testing and replacing mine.

They had plenty in stock at the dealership I used as well. Although they didn't have any at the online place I usually buy through so that was a bit curious. My car has been running pretty well for almost a month now so I feel pretty confident that was the resolution of that issue (I hope).
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Old 07-29-2007, 02:27 PM   #23
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Is this a known or common issue affecting the 01 Legacies?
I just bought a used 2001 Legacy L wagon, and am keeping an eye out for any potential issues.

Thanks.
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Old 08-12-2007, 10:01 PM   #24
zzzzzzzz
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IT WORKED!!!!!!!! I hope....

So I just replaced the a/f sensor yesterday (P/N: 22791AA00A). It took so long because I only had a 2 ton jack and no stands and wasn't confident enough to do it (though I did try and just couldn't remove it because I had no tools). So yesterday, I went to a friend's shop and did the work there. Here's what I did to replace:
1. Ramped the car up to eye level.
2. Unbolt the heat shield that was just south of the sensor. There are QTY4 12mm nut and QTY1 10mm nut. Semi-tight so use a long ratchet and a regular one to hold the bolt on the top/opposite side.
3. Once unbolted, slide the shield up a little up front. You won't be able to slide it completely off because of the sensor's wire.
4. This should now give you enough clearance to slide a 22mm open ended wrench onto the sensor. I thought it may be tough to remove, given the car is now 6 years old and the thing is part of the exhaust sys w/ all that heat, but it loosened up fairly easily; probably because the anti-seize hadn't dried up like I thought it may have.
5. Replace the sensor w/ the new one.
6. Reset the ECU using the ol' uplugging ground off the battery for half and hour.
The CEL stayed on even after I replaced the sensor and resetted the ECU, but after driving it last night, and I think turning the ignition off and on several time on separate occasions, the CEL disappeared (imagine my sigh of relief!). So today, I drove the car around all day for ~50 miles, accelerating, passing at 70, uphill, quick start, going to 7k rpms, just trying to see if the problem comes back.

Nothing!

I'll commute w/ this car for the next week and see if the problem comes back. I really hope this nips it! Wish me luck. Thanks MkIII, if this works of course.
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Old 08-13-2007, 09:48 AM   #25
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What you are describing, and looking at the diagrams - looks to me completely like an O2 sensor - not and AF sensor?
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