Author Topic: Shaking/shuddering at low speeds/RPMS and occasional stalling issue is back  (Read 1714 times)

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Offline Polaris

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Hey everyone, after the last time this happened a few months ago and topping the car up with ATF the car has run pretty much like a dream, but would still shudder/stall out if I reversed slowly up a hill (for example reversing out of Jackie's parking lot haha). Car drives completely fine otherwise, acceleration feels fine, etc. Today the issue happened again when I was "coasting" without giving it gas into a car wash stall, and the car stalled out. Symptoms seem similar to these two threads, but I don't have any sputtering or stalling at high speeds, this is basically exclusively a problem when I'm in a parking lot coasting around or I coast up to a red light.

http://www.westernsubaruclub.com/smf/index.php?topic=53400.0

http://www.westernsubaruclub.com/smf/index.php?topic=53479.0

Things I have done is look at the A/F ratio on the AP, clean the MAF sensor, check transmission fluid level and appearance (looks decent to me), and check the air filter. Things I have not done yet is just go to Jackie for a ATF change/flush, and maybe see if there are any metal shavings or something in there that might indicate the transmission is screwed? Spark plugs were changed recently, throttle body was cleaned, etc. and I don't think I have a vacuum leak.

The major problem is that I can't seem to be able to reproduce this problem consistently. I've taken it to Jackie and tried to reproduce it to no avail, and last time I was at Subaru for the airbag recall I told them about it and they checked it out and couldn't find any problems either and couldn't recreate the problem. It's super rare that it happens, but I guess it's "consistently" rare, like I can count on this problem happening at least once out of a few times I drive, but I can't predict when it happens, because sometimes it happens when I'm going up a hill, sometimes just on flat ground, sometimes it doesn't happen at all.

Googling as well as searching on LGT, and looking at suggestions made by other members on here, it seems like the various possibilities include front o2 sensor needs changing, torque converter may be bad, fuel pump is bad, oil control valve problem, vacuum leak, or transmission is about to blow up and I'll be out a few grand.

There isn't a check engine light, and just like a few months ago there are no codes when I scan it. It's super intermittent and if I brake/give it gas the problem starts so I know how to "get rid of it", I just don't want this to be the start of a big problem that costs me a lot in the future/just want to fix it before it gets bad.

Thank you so much for your help!

Offline SlowLGT

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Did it feel like a misfire? I had a misfire issue that made the car act very strange, and also did not trip any CEL.

Offline Polaris

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Did it feel like a misfire? I had a misfire issue that made the car act very strange, and also did not trip any CEL.

Hm, not exactly sure what a misfire would feel like; what should I be monitoring/looking at to see if a misfire is happening, and where the misfire is at? Thanks!


Small update, I made a post on the LGT forums and so far 3 other people have expressed that their car had very similar problems and they haven't managed to diagnose it yet. Googling previously also seems to show other people having similar problems and either didn't resolve it, or resolved it with things that I've tried but didn't work :(

Offline Bristolian

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Alternator on the way out maybe?
If in doubt, flat out !

Offline lophilip

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try cleaning throttle body.

Offline diamondedge

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try cleaning throttle body.

I'm going to +1 this, I'm leaning this way too.

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Offline Valkyrie

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subarus are stupid finicky with A/F issues and i have a hard time believing your issue is air, spark or fuel related without a CEL showing up. I agree with poster about Alternator. Sounds like a charging system issue. Most likely Alternator not charging the battery enough. Try checking to see if the V belt is tensioned properly bring up the voltmeter on your AP to see if your charging around 14.5 at idle.

All other things you listed would throw a CEL