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Hi guys, I'm having a problem that's occurring when I accelerate. Its mostly felt at lower speeds and when going uphill. Its felt at all RPMs. Its not felt when going downhill.

'00 Outback EJ25 4EAT.

Originally I took it to my local garage to ask him for a quote to repair or replace the transmission (been having some gear changes that are heavy and sometimes it seems not to know what gear to be in) and also to look at my oil leak which I thought was camseals. Also asked him to look into the rattle coming from under the car. Before taking it in there was no shake.

Went back and he'd gone and put an additive into the transmission to make it change smoother, replaced the oil filter because he said that was the oil leak source and had welded part of the exhaust to stop the rattle. Drove off and the rattle was still present.

Next day went back and he did some more welding which had stopped the rattle. Whilst there he also took the liberty of degreasing my engine.

On the same day as the degreasing I had a puncture repaired and my tyres rotated at my tire guy, next door to the mechanics.

After picking up the car there is now a shake, not felt through the steering wheel, when I accelerate. Took it back to tyre guys to check the balancing and the tires are balanced. Still shaking. Took it back to tyre guys again (I thought it must be tyres) and had alignment done but that was ok too.

Sorry for long story, my questions are:

Could it be my original transmission fault getting worse? When I flick it into neutral and roll it goes away.

Could the degreasing of the engine buggered something up? If so, what?

Could the additive be the problem?

Could rotating the tyres cause such a shake?

Could it be axles? (it'd be a coincidence if it went the same time but my research here point to maybe)

Is my mechanic a muppet? I'm leaning towards yes on this one.

Thanks for your thoughts, its driving me nuts.
 

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Are all four tires the same brand, model, size and tread depth?

Vibration only under acceleration, as you described it, is sometimes caused by a bad joint in the rear propeller shaft, or a bad joint in one of the axles.

As the vibration seems to have started just after the tire rotation, have you tried returning the wheels to their original position to see if the vibration continues?

How bad was the puncture? Did you drive on the deflated tire for any distance?

If the car has the 4-speed automatic, try inserting the AWD disabling fuse (FWD fuse). This will put the car into FWD mode, so that driving torque is not being applied to the rear drive train. Try it this way and see if the symptom is still present. If not, then at least the area has been narrowed down.
 

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Some suspects

Is my mechanic a muppet? I'm leaning towards yes on this one.
Do any of these pictures look like your mechanics?
94px-OscarHardhatPVC.jpg 94px-BigBirdHatHankyPVC.jpg 139px-ElmoMechanicPVC.jpg 109px-CookieMonsterMechanicPVC.jpg

Check the torque on your lug nuts as well. De-greasing may have impacted an electrical component which controls how the engine runs or accelerates. I don't think welding a wonky heat shield will affect anything, but you might have look to see if he heated something nearby - wire, 02 sensor, U-joint bushing. Let us know about it, oh and which one looks the most like your mechanic.
 

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Discussion Starter #4
The tires are 2 different brands, same size with similar tread. I had a nail in one which didn't actually deflate it so didn't drive on it flat.

I thought about putting them back to their original positions but if I can roll in neutral without any shaking then doesn't that rule out the tires as the problem?

I have just put it into FWD with the fuse and the problem is still present, so its a front end issue right?

The lug nuts have all been torqued when the re check was done on the balancing.

Will have a good look to see for fried sensors or wires.

My mechanic is definitely the one living out of the trash can.
 

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Could also be that you are running just on 3 cylinders upon acceleration... check and clean (or replace) the spark plugs!
 

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Check the continuity of the wires while you're at it. I swore I had a transmission problem at about 130K Miles because it seemed to be searching for the correct gear and hesitating when trying to accelerate. Luckily I got a P0302 check engine light (CEL) code that told me I was having a second cylinder miss-fire. After new plugs and wires she ran like new. Is or has your CEL been on?

These symmetrical AWDs are really finicky about their tires. It's best to run all four corners on the same brand or at least with nearly the same amount of wear in circumference (within 1/4" or about 6 mm).

I'm not big believer in "Miracle-in-a-can" type additives. It may not have hurt, but I'd be surprised how much it would really help unless the tranny fluid was clean to begin with. Check out this link: http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/5843-changing-automatic-transmission-fluid-easy.html

BTW, the Muppet in the trash can is known as "Oscar the Grouch" here in the US of A. I hope your mechanic is in a better mode than that dude.
 

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Should have asked about warning lights in the dash on, or flashing.

I have just put it into FWD with the fuse and the problem is still present, so its a front end issue right?
Possible but not necessary. The transfer clutch could be binding mechanically.

Also, if the car is driven in a tight circle on a paved, flat, surface, at idle, does it go around on its own, or very little throttle, does it hesitate? (This should be tried with the fuse out and with it in.) If the clutch is binding, this could lead to vibration when the car is accelerating with different circumference tires, and would lead to the hesitation symptom ("torque bind") when turning. (Do a search for "torque bind" -- lots of posts to read.)

Otherwise, the front end would be the place to look -- front axles/joints.

The possible causes of vibration are many . . .
 

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Discussion Starter #8
An update on this;

There were no error codes. I had a look round for toasted sensors but didnt see any.

The problem became intermittent. Sometimes on the same journey but usually when I started out there was no problem, then as it heated up(?) the shaking began. Although sometimes it was present from the start of the journey.

I had a lovely read about torque-bind and was so happy to hear about another problem my car could have! Did the figure 8 test but it showed no sign of hesitation and went round with minimal if any gas.

I have reset all tires to their original position as the front two had different tread patterns, as did the rear. Now the front match and the rears match, not ideal I know but better than before. Changed my rear pads while I was there.

Inspected the front half shafts whilst I was in there and noticed a small amount of play in them when wiggled up and down. Maybe a couple of mm. Is that within normal limits?

Checked continuity in the spark plug leads with Ohm meter. They read around 7 Ohm for the short ones and around 9 Ohm for the longer. Can anyone tell me if that's normal?

Took out and cleaned up the spark plugs. Noticed one had a crack in the ceramic part, like a black line running up two sides of it. Bought a replacement one for the price of a thoroughbred racehorse(!) and fitted it.

Did an oil and filter change.

Drove it home from my mates and it felt good, although as I mentioned it went intermittent so I'm not getting too hopeful too soon.

Will update again in a few days, if you know about the leads resistance and half shafts please feel free.

Thanks.
 

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Hi guys, I'm having a problem that's occurring when I accelerate. Its mostly felt at lower speeds and when going uphill. Its felt at all RPMs. Its not felt when going downhill.
This is *classic* inner DOJ front CV axle symptoms. That would be the first thing to ask and check based on your symptoms, I'm surprised that isn't being checked.

Have the axles ever been replaced?
Have the boots ever been replaced?

At this age (and what's your mileage?), it would be very rare to still have the original boots on the car - the passengers side inner DOJ boot is usually the first to go due to it's proximity to the exhaust and associated heat.

If the axles have ever been replaced with aftermarket then that's probably the issue - new aftermarket axles are plagued with issues (any car forum or google search will show it). If they were rebooted then I'd be scratching my head and doing some more investigating.

In general it is advised to never install aftermarket axles, they are by and large prone to a lot of issues, including vibration when accelerating. proper axle repair that has high success rates and doesn't waste your time goes in this order, with the first 3 being near %100 success rates:

1. reboot your original Subaru axles all the time, never replace them no matter what sob story a mechanic gives you
2. if you have to buy another axle get a used OEM Subaru axle (green cups) and reboot it.
3. if you have to buy new get one from MWE
4. if the shipping/core bothers you then the only acceptable high percentage solution is an EMPI axle which you can order online for a reasonable price - like $60 or so.

The minor play you describe sounds normal, they aren't rigid and as such have some play like that. If both sides are the same I would assume it's normal.
 

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And for future refernce, if the spark plug wires are old, just replace them with subaru units. An om meter does nothing to tell you if the insulation has broken down to allow for volatge leakage. However the sparklies test does. Mist the wires with water while the engine is running at dusk or early evening and look for sparklies.
 

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Discussion Starter #11
Just an update to say that the shaking is gone completely.

Obviously I did all the repairs at once so not sure which fixed it but my thoughts are that the cracked spark plug may have been the main cause so it was worth the effort taking them out to check and clean them.

Thanks for all your help and suggestions guys.
 
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