Jerky acceleration

For the older twin turbo B4 models

Jerky acceleration

Postby RSK20 » Mon Mar 18, 2013 6:32 pm

My Legacy is very jerky on acceleration and deceleration in a super-sensitive way that I can't smooth out. It's not so much a clutch-engagement issue (as far as I can tell) as it is a throttle issue. When I let off the accelerator in gear, the driveline is noticeable thumpy and jerky. When I accelerate in gear it jerks again. It's far more pronounced in lower gears/revs, especially in stop and go traffic. Car has a new clutch, and the gearbox oil had been replaced. Is this likely to be a problem with the universal joints in the driveshaft?

UPDATE: The MAF sensor was playing up. A new one from Subaru has solved the problem :)
Last edited by RSK20 on Thu May 16, 2013 6:54 pm, edited 2 times in total.
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Re: Jerky acceleration

Postby BUDDAH » Mon Mar 18, 2013 7:10 pm

Forum experts will be here soon but in the mean time its impossible to tell without driving it :wink:
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Re: Jerky acceleration

Postby Jack_Keaka » Mon Mar 18, 2013 8:01 pm

our cars are notoriously jerky. best advice is: learn to clutch it more to make it smoother.
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Re: Jerky acceleration

Postby BUDDAH » Mon Mar 18, 2013 8:07 pm

Jack_Keaka wrote:our cars are notoriously jerky. best advice is: learn to clutch it more to make it smoother.





:roll:
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Re: Jerky acceleration

Postby Dropz » Mon Mar 18, 2013 8:09 pm

If theres a delay in the jerk then there is excessive backlash somewhere, otherwise it is probably the normal driveline shock. try slipping the clutch a bit.
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Re: Jerky acceleration

Postby BUDDAH » Mon Mar 18, 2013 8:10 pm

Dropz wrote:If theres a delay in the jerk then there is excessive backlash somewhere, otherwise it is probably the normal driveline shock. try slipping the clutch a
bit.




:roll:
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Re: Jerky acceleration

Postby Jack_Keaka » Mon Mar 18, 2013 8:12 pm

BUDDAH wrote:
Jack_Keaka wrote:our cars are notoriously jerky. best advice is: learn to clutch it more to make it smoother.


:roll:


constructive and useful information BUDDAH. your input to this forum is greatly appreciated and in no way annoying.
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Re: Jerky acceleration

Postby BUDDAH » Mon Mar 18, 2013 8:15 pm

Jack_Keaka wrote:
BUDDAH wrote:
Jack_Keaka wrote:our cars are notoriously jerky. best advice is: learn to clutch it more to make it smoother.


:roll:


constructive and useful information BUDDAH. your input to this forum is greatly appreciated and in no way annoying.





Did you read the OPs post ??


its impossible to tell without driving it


I once owned a B4 and the clutch was perfect and the gear box was sweet it was possible to go through 1st to 5th without a clutch. I 100% doubt the OP clutc is the problem :wink:
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Re: Jerky acceleration

Postby bates91 » Mon Mar 18, 2013 8:49 pm

gearbox mounts, engine mounts, rear diff mounts, suspension bushings..???
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Re: Jerky acceleration

Postby BUDDAH » Mon Mar 18, 2013 8:54 pm

bates91 wrote:gearbox mounts, engine mounts, rear diff mounts, suspension bushings..???





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Re: Jerky acceleration

Postby garbo41610 » Mon Mar 18, 2013 9:34 pm

BUDDAH wrote:
bates91 wrote:gearbox mounts, engine mounts, rear diff mounts, suspension bushings..???





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:lol: :lol:

I'm sorry, but that's f***ing funny. You sir, may be a twat, but a f***ing funny twat.
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Re: Jerky acceleration

Postby migoreng » Tue Mar 19, 2013 2:16 pm

Just spend that extra half second every time to smooth out your clutch and throttle operation. :p
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Re: Jerky acceleration

Postby redeemed » Tue Mar 19, 2013 11:11 pm

Jack_Keaka wrote:
BUDDAH wrote:
Jack_Keaka wrote:our cars are notoriously jerky. best advice is: learn to clutch it more to make it smoother.


:roll:


constructive and useful information BUDDAH. your input to this forum is greatly appreciated and in no way annoying.

My sarcasm detector is going off ever so slightly ... :lol:

But seriously, seeing a couple of Gen 3 owners mention this makes me wonder - Is driveline slack really that common? I gave a fairly car-savvy friend a lift home the other day, and he mentioned it might be wobbly/loose driveshafts? For me, it's a very noticeable CLUNK when changing throttle position, i.e. taking my foot off causes it, and so does putting my foot down, even gently. I'm getting sick of it :angry2:

On the other hand... it might be exacerbated by the throttle that does this weird thing where revs jump straight up by 500 rpm. No matter how gently I try to depress the accelrator, revs always jump by 500, never smoothly... something even a 15 year old Ford Festiva can do :evil: funny throttle + possible loose bits in the driveline = :angry2:

BUDDAH wrote:
bates91 wrote:gearbox mounts, engine mounts, rear diff mounts, suspension bushings..???





Stop bulbs , seat belt mounts , flat tyre, worn mats, crook paint job, stuck CD in head unit , rainy day ----------- ------------- ---------------

:lol: :lol:
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Re: Jerky acceleration

Postby migoreng » Wed Mar 20, 2013 8:07 pm

Yes. My throttle appears to be much more sensitive compared to my old car.

I tend to take off at 1000rpm with a tap of the throttle. If I try a bit harder I can manage to take off with the revs at 600 or so without any shuddering...

I'm not sure if its just me but I've noticed the tacho does lag behind the engine sound slightly... I clutch in, release the throttle but the revs maintain for a quick moment. Or sometimes the revs even jump slightly. I guess I've gotta practise more as I'm used to the Honda Prelude gear box...

I'm trying to make sure my foot is completely off the throttle when changing gears.
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Re: Jerky acceleration

Postby C-Shell » Sat Mar 30, 2013 12:31 pm

I have what sounds to be the same problem in my Gen 3 RX.

The best thing I've found to reduce it is the the gearbox and diff oil. I am using a full synthetic Nulon oil w/ the Nulon G70 additive in both (http://www.nulon.com.au/products/Specia ... VZNalf-nbw) I have replaced the rear diff and outrigger bushing which made the slop a lot tighter, but didn't make anywhere near the difference that the oils did. Make sure when your changing gears hard and fast that you don't just dump the clutch and get that big thump sound, is a good way to fasten up the backlash from gear wear and tear. You could try getting some Group N transmission and engine mounts, but this would probably increase NVH a fair bit.
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