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 Post subject: Low speed/rpm stumbling and sputtering
PostPosted: Tue Aug 31, 2010 2:42 pm 
"FNG"
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Hi guys, I've got a little bit of an issue with my '99 Outback 2.5 5-speed. Over the last month or so it has begun to run worse and worse, the idle is often erratic (up and down, up and down) and very rough and when the car has sat for a day or so, or its only sat for 20 mins (still warm) when you try to accelerate calmly it stumbles and falls on it face, and if you hit the gas hard it will jerk back to life and take off. It also like to jerk when slowing down alot (coasting in gear).

I've replaced the spark plugs, front O2 sensor, run fuel system cleaner and sea-foam through it, and I'm running 93 octane.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Tue Aug 31, 2010 4:49 pm 
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Sounds like your Idle Air Control valve is acting up, or your MAF sensor needs a clean. You shouldnt run 93 octane either, you're just pouring money down the toilet. 87 or 91, 93 is overkill.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Tue Aug 31, 2010 7:57 pm 
"FNG"
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Thanks for the response, I forgot to mention that I did already clean the MAF sensor with proper MAF cleaner too. I will check out the IAC valve as soon as I get a chance, it probably needs cleaning at the very least.

On a separate note, but still about the same problem, I asked a Subaru guy about my problem, and he said to check the Crank Position sensor, I did, and I noticed two things, 1: It was cracked where it is fastened down with the bolt, and after removing it it noticed that there was black residue on the bottom of the sensor. I went ahead and replaced it because it was only $22 at the local Autozone and at 127,000+ it looked as if it had never been replaced before.

It does seem to run better, but the main issue that I had before was hit-and-miss, so I will keep everyone updated.

Thanks again, this seems like a pretty great forum so far!



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 12:12 am 
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Is the check engine light on?

If so, thats a good place to start.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 10:08 am 
"FNG"
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Nope, no CEL, I wish I had one; I have a code scanner so its easy enough for me to run the codes. After a drive yesterday it seems as if the car does run better with the new crank sensor, but the problem still exists. I'm still going to pull the IAC valve and check that, but beyond that I'm stumped.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 11:04 am 
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Sounds like IAC to me. Had it happen on my Saab especially if it is sporadic. I found that I could replicate it by Running it hard then coming to a stop and would often shut off after that.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 11:53 am 
"FNG"
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Hopefully ill have a chance to check and clean it today, im hoping thats all it is. My issue seems to only be of major concern when i first start it and drive at about 1500 rpms in first or second. Its violent then to the point where the car is bucking and jerking so hard that the tires will chirp. It does stop if i floor it and go through the rev band a bit.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 7:32 pm 
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Definitely check the IAC and the MAF. You can clean the MAF with MAF cleaner from autozone or something. And yeah.. don't use 93. Huge waste of money.. and its actually making your car perform WORSE then using 87. Your car is tuned for 87, so if you are using 93.. its not using the fuel properly.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 02, 2010 11:18 pm 
"FNG"
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I cleaned the IAC today, I thoroughly sprayed it with throttle body cleaner, (even stuck the little hose inside and blasted), I'll give an update on that soon. And I have already cleaned the MAF with MAF cleaner from Auto-zone. The only reason I've kept running the 93 is because my mileage increased (approx. 22.5 to 23.5) and it has seemed to run better since I started using it.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Sep 03, 2010 8:59 pm 
"FNG"
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Well after driving the car a bit, the problem is still there. Its no better, and its still sputtering and stalling at the same exact time, and it still has the wildly fluctuating idle. I am beginning to run out of ideas, I thought of just replacing the IAC until I saw that it costs $350 at the local parts store.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Sep 03, 2010 10:48 pm 
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It could be your throttle position sensor. Hook up an OBD-II reader to it and check the throttle reading and see if it's sitting at 0% like it's supposed to, and going up to 100% when you push down the accelerator. It may just be out of adjustment/calibration even.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Sat Sep 04, 2010 12:23 pm 
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I have an OBD-ll scanner but its just a basic one that only reads the codes, and doesnt even tell you what they are. Would the code readers they have for free use at parts places be able to read that?



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Mon Sep 06, 2010 2:31 pm 
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No, the ones they use at the parts places usually also just read codes and tell you what they are - no real time data. You can definitely buy such a scanner at most part stores but they're usually overpriced - like $150 vs. <$80 on Amazon.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Mon Sep 06, 2010 3:07 pm 
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jey wrote:
No, the ones they use at the parts places usually also just read codes and tell you what they are - no real time data. You can definitely buy such a scanner at most part stores but they're usually overpriced - like $150 vs. <$80 on Amazon.



do you have one that you would recommend? Is there one that can be placed in dash like in the pocket below the CD player?

I have looked around but cannot find an in dash one.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Mon Sep 06, 2010 3:45 pm 
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^^ I can answer that. Scan Gauge. They can read check engine codes, and they also give TONS of real time data, from almost every sensor. On top of all that they also give fuel economy, both instant and average, and they give horsepower.

http://www.scangauge.com/products/



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Mon Sep 06, 2010 8:47 pm 
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heh, I just found that lol I was coming here to update the post.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Tue Sep 28, 2010 7:24 pm 
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Ok, heres an update, I never did buy a scan gauge or nice code reader, don't have the money (poor college kid). But something new has happened, over the last few days I've done alot of highway driving 1200 or so miles at 70+ mph, and after my last fill-up back in town it did it worse that ever, it lasted a long time, and I couldn't get it to pull out of it, the more I stepped on the gas, the more it would fall on its face, it happened when the car was still warm, after it sat for a couple mins off, and then re-started. The upstream 02 sensor is replaced, the plugs are replaced with Bosch, the IAC was cleaned etc etc, nothing helped. But after this last time, I managed three CEL codes.

P0130: Upstream O2 sensor or circuit malfunction
P0135: Upstream O2 sensor heater circuit malfunction
P0141: Downstream O2 sensor heater circuit malfunction

I'm not sure whether the codes indicate the problem, or were a result of the car running poorly, but my interest in fixing this issue is renewed.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Tue Sep 28, 2010 9:22 pm 
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So are these codes new, or from the old problem?
If they are old, reset the car and see if you get new codes. When the light comes on, pull the codes immediately, and let us know.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Wed Sep 29, 2010 8:43 am 
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What part did you use when you replaced the O2 sensor? If you spliced in an generic sensor you should double-check your wiring.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Wed Sep 29, 2010 9:43 am 
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Huffer wrote:
So are these codes new, or from the old problem?
If they are old, reset the car and see if you get new codes. When the light comes on, pull the codes immediately, and let us know.


These are codes as of yesterday, 2 hours before I posted the last update. I have never had any CELs before so thats why I posted the update.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Wed Sep 29, 2010 9:46 am 
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jey wrote:
What part did you use when you replaced the O2 sensor? If you spliced in an generic sensor you should double-check your wiring.


I used a direct-fit OEM style O2 sensor, with the plug already wired on.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 30, 2010 10:06 am 
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Inspect the wiring of the O2 sensor, all the way from the sensor to the front. It could have come out of it's original routing and sat on the exhaust, melting all the wires. I've had that happen before, entire O2 sensor was shorted :lol:



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Thu Sep 30, 2010 10:30 am 
"FNG"
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Checked the wiring, all is good, nothing melted, checked the plugs and sensor to make sure the wires were attached properly and they are. This is definitely one pain in the butt problem!



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 8:03 am 
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Sounds almost like a fuel pump problem to me.. but its throwing some weird codes.

Have you tried unplugging the MAF sensor yet and trying to run the car and see what it does?

The erratic idle and stuff makes it sound like a MAF problem. But the way it sounds like its acting almost sounds like a fuel pump problem. Especially the jerking around upon acceleration, etc. Does the engine seem to be running hotter then normal? Check that out as well.. could be signs of a fuel problem.

Just some ideas to consider.

Edit: Found another thread where someone was throwing weird codes, and it turned out to be a fuel pump:

viewtopic.php?f=11&t=14519

I'm guessing its the fuel pump on its way out..



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 8:18 am 
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d1giPhux wrote:
Sounds almost like a fuel pump problem to me....



I thought this too, as well as thinking there might be a hole in the intake tubing somewhere.

OP, Is there a way that you can get a video/sound clip of this? Also check the plug wires... lightly spray them with water to see if there is any sparks. Cracked or bad wires would also be one of the symptoms of a car bucking. Petrified (stiff) wires are also a result of a bad position sensor.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 9:59 am 
"FNG"
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As soon as I get a chance I will get a video of it, its not always easy though, sometimes it will do it a ton, other times I cant get it do it. I'll try the plug wire trick, and the fuel pump is another story.

There is definitely something wrong with the fuel system in that, there is no venting, it takes me 10-15 mins to fill the car from empty because the pump constantly clicks off even with a very slow stream, one time after an hour of stop and go traffic jam in 90+ heat I pulled into a gas station to fill and when I took of the gas cap I could hear the release of pressure. The gas gause is also very erratic, until approx. half to 1/4 tank the guage reads wherever it feels like, from empty to full and all inbetween, once the actual level gets to half-1/4 though, it reads accurately.

On a fill-up once I pulled ALL of the hoses off of the charcoal canister in front of the back bumper and saw no difference so that is eliminated, other than that I haven't wanted to take the car apart for something that is a minor nuisance, since its my only mode of transportation.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 10:11 am 
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Your vent control solenoid under the bread box in the rear needs to be replaced. I've had to do it on BOTH of my 99 LGTs. Thats whats causing that vent / fuel refill click problem 99.9% guarantee. Could be causing you other problems as well.

Your acceleration problem / jerkiness problem and such seems like a fuel pump issue. Just fixed this on a friends RAV4 that would do the same thing. The fuel pump MAY NOT be dead.. but intermittently working, causing you the jerking back and forth and such.

If you need the vent solenoid part number.. i'm sure I could find it somewhere for you amongst my paperwork. Its not too expensive, and it will fix your fuel re-fill / venting problems.

http://opposedforces.com/parts/legacy/u ... tration_6/



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 1:04 pm 
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If its not too much of a hassle, and you could find the part number that would be great. Btw, what is the bread box and what does the solenoid look like? I would LOVE to fix that.



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 1:23 pm 
SLi O.G.
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bread box = charcoal canister

and the 'vent control solenoid' as i like to call it, the proper name is 'rear vent solenoid valve' and the problem is that they get stuck open / closed or something like that. you might be able to just take it out and fix it. Here is the part number:

vent solenoid valve part # : 42084FA120

The bread box is #25 on this chart, and the 'vent solenoid valve' the part you need to replace, is #21.

Image

another picture of the valve can be found here:

http://www.subarupartsforyou.com/cp_par ... rtid=12556



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 Post subject: Re: Low speed/rpm stumbling and sputtering
PostPosted: Fri Oct 01, 2010 3:49 pm 
"FNG"
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Ahh, that thing! :smile: On that same fill-up when I unhooked the charcoal canister lines, I also unhooked the hoses to that as well.



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