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2001 Legacy/Outback Shaking at Highway Speeds: Help!

16 messages,  Last post on Oct 05, 2010 at 7:48 PM

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What is this discussion about? Subaru Legacy, Subaru Outback, Engine, Fuel System, Steering, Suspension, Sedan, Wagon

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#1 of 16 2001 Legacy/Outback Shaking at Highway Speeds: Help! by booba2

Sep 01, 2010 (9:48 am)

Help! I have a 2001 Subaru Outback. When I drive at highway speeds, my car will begin to shake. I can hear the engine working harder and it just rides rough in general. It comes on slowly and goes away slowly on its own. It seems to do this more frequently when I use regular as opposed to mid grade gas.
 
In the last year, I have had my head gaskets redone, a new driveshaft put in, new spark plugs and wires, and a new knock sensor. I do not have a lot of money to spend on getting this diagnosed or fixed, so if anyone knows anything that can help me, I would greatly appreciate the information. Thanks.

#2 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by ateixeira

Sep 01, 2010 (9:51 am)

Replying to: booba2 (Sep 01, 2010 9:48 am)
No check-engine light?
 
Next thing I was thinking was the ignition coil, but unburned fuel should trigger a CEL.

#3 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by xwesx

Sep 01, 2010 (10:38 am)

Replying to: booba2 (Sep 01, 2010 9:48 am)
Shaking.... like the something is out of balance? Usually, if the engine, it will come across as a vibration. If it were something in the wheels, steering, driveshaft, etc., it would actually feel like a shake - so, I guess, more intense/violent.
 
Taking a WAG by your description, I suspect the driveshaft is out of balance; probably something to do with the center bearing or the bushing surrounding it. Did the problem happen before your had your driveshaft replaced, or only since?
 
I had something similar happen on a '96 Outback, but it only manifested itself in high-torque situations, such as when accelerating hard, while turning, coming from a stop (like taking a right turn from a stop light). The car would shake a little, plus I would hear a LOUD thumping from under the car. I replaced the front half of the driveshaft and all was well. The rubber bushing that surrounds the center bearing had begun to fail.

#4 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [xwesx] by booba2

Sep 02, 2010 (7:13 am)

Replying to: xwesx (Sep 01, 2010 10:38 am)
This shaking started before the driveshaft was replaced...actually it was going on for a while and I was putting off taking it in until I heard a loud "clunk clunk" when I started from a stop. That's when I decided I couldn't wait any longer and took it in...I thought that the whole thing was connected, but I guess not since the "clunk clunk" went away after a new driveshaft, but not the problem on the highway.
 
In response to the first response: no check engine light on. I suppose it is possible that the actual bulb for the check engine light burned out, but doubtful.

#5 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by ateixeira

Sep 02, 2010 (8:30 am)

Replying to: booba2 (Sep 02, 2010 7:13 am)
Check that light - when you insert the key a test sequence should light it up.
 
If it's burned out I'd get a code reader and pull the codes.

#6 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by xwesx

Sep 02, 2010 (9:36 am)

Replying to: booba2 (Sep 02, 2010 7:13 am)
Okay. That "clunk clunk" was probably the same issue I had with mine, so replacement of the front half of the driveshaft (which includes the bushing & bearing) would have resolved that.

#7 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [ateixeira] by booba2

Sep 08, 2010 (1:41 pm)

Replying to: ateixeira (Sep 02, 2010 8:30 am)
I checked that light and it isn't burned out. I asked about fuel system cleaners at an auto parts store and got one to try. The man there said that many Subarus call for premium octane gas, so he suggested that I let it get really low, then add the cleaner with a full tank of premium and see what happens. I figured it couldn't hurt and buying one can of cleaner is much cheaper than just having it looked at.

#8 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by ateixeira

Sep 09, 2010 (9:53 am)

Replying to: booba2 (Sep 08, 2010 1:41 pm)
OK, let us know if that makes a difference.

#9 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [ateixeira] by booba2

Sep 20, 2010 (1:37 pm)

Replying to: ateixeira (Sep 09, 2010 9:53 am)
Well, I thought it was making a difference, but I was mistaken. It shook on the way to work twice now since I put in the cleaner and premium fuel, so now I feel like I am back to square one.

#10 of 16 Re: 2001 Legacy/Outback Shaking at Highway Speeds: Help! [booba2] by fibber2

Sep 25, 2010 (5:38 pm)

Replying to: booba2 (Sep 20, 2010 1:37 pm)
I just read thru the posts. It just suddenly happens when you are driving at some moderate speed steady state, when you are accelerating, or only at very high speeds? We need more on the conditions.
 
Automatic or manual?
 
When it suddenly begins happening, try shifting into neutral (or if manual, depress the clutch). Note - only do this when you are alone on the road - not in traffic! If it is related to balance of a half shaft or center drive shaft, it should continue to shake even as the engine rpm dies off to idle. If it stops abruptly, it is more likely an engine/tranny problem.

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