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jerky On/Off throttle, fix?


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#1 Adictions

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Posted 18 March 2015 - 05:05 PM

Hi guys, my Gen 3 outback manual has a problem when coming on and of throttle, when i apply the throttle in gear the car seems to leap or jerk forward before settling itself, the opposite thing happens when coming of. Also when slowly rolling down a slope such as a roof car park in gear without accelerating it will jerk forward and back. Sometimes when this happens i can hear squeaking coming from below the shifter, this makes me think it may be the trans mounts, am I right? what else could it be? i have had a looked for any movement in uni joints thinking they could be really slack but they all seem fine.


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#2 migoreng

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Posted 18 March 2015 - 05:53 PM

I believe it could be mounts.

My liberty b4 does the same in say 1st or second...

i can for example accelerate in 2nd to the mid rpm range lift off the throttle and the whole car jerks or bounces a few times.

With smooth throttle control i can reduce it. I will eventually take my car to ichiban for repairs.

#3 glenisanutter

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Posted 18 March 2015 - 07:21 PM

On the down hill i get the jerky movement if my foot is resting on the gas pedal.. if i lift 100% it stops!

as for the acceleration side i cant help!



#4 crjohnson

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Posted 19 March 2015 - 09:02 PM

My 2003 outback manual has the same problem. I've tried a couple of things but so far nothing has really helped!

 

- diff bushes, both front and rear replaced with whiteline bushes

- trailing arm - lower front bushes. replaced with whitelines again.

 

Next on the list is trans and engine mounts, might be a good idea for you to check there first since my mods have done nothing?

 

One thing I have noticed after doing the trailing arm bushes is that there is a noticeable noise (like metal-to-metal clunk) when going on/off the throttle now. Note sure what it could be but i'll try find something and let you know!



#5 Jizanthapus

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Posted 19 March 2015 - 09:41 PM

My GEN3 Liberty had the same problem. I replaced the gearbox and the problem went away for a while although it appears to be back again. It could be a number of things including:

 

- Universal joint on the tailshaft

- Engine mounts

- Gearbox mounts

- Diff or gearbox issue

 

I'd start with the cheaper things and work your way up. 



#6 crjohnson

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Posted 20 March 2015 - 06:56 AM

Replaced the entire gearbox or just the mount? Strange if it was the whole gearbox, but yea I am also wanting to compare the amount of play in the tailshaft and compare it to a mates impreza (which has no jerk..). 

 

Also bought some wrx engine mounts only minutes after my last post so will let you know if they make a difference. 



#7 Adictions

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Posted 20 March 2015 - 11:46 AM

Let me know how you go johnson

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#8 Jizanthapus

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Posted 20 March 2015 - 01:15 PM

Replaced the entire gearbox or just the mount? Strange if it was the whole gearbox, but yea I am also wanting to compare the amount of play in the tailshaft and compare it to a mates impreza (which has no jerk..). 

 

Also bought some wrx engine mounts only minutes after my last post so will let you know if they make a difference. 

 

I replaced the whole gearbox. I haven't replaced any mounts or joints as of yet.



#9 El_Freddo

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Posted 20 March 2015 - 04:47 PM

A mate of mine has the same issue with his (mildly) modified Gen II Liberty with H6 conversion.  He's replaced just about every bush you can imagine, swapped to another gearbox, has a new clutch and it's still there.

There is either something in the design of the drive train of subarus as my L series with EJ22 does it too, but only at low speed in the car park where I disengage and reengage the clutch to solve the problem.  Or the other thought is that it's in the engine management at that low throttle/low vehicle speed where everything is very sensitive.

What I'm wondering is if the spring load in the clutch disc is too light for the vehicles it's used in today.  While a brand new clutch plate might have great spring rating when new, as time goes on these springs can become worn out much like our suspension springs can sag.  An upgraded spring might be the way to go, I really don't know and nor do I know how to go about getting a custom one done as all kits just refer to the clamping pressure of the pressure plate in Heavy Duty applications.  These are the springs I'm referring to:

 

p7310520.jpg

 

Another mate of mine sold his Outback because he was over the issue!  That thread page thread of his can be read here.

 

Cheers

Bennie

 


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#10 duncanm

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Posted 20 March 2015 - 05:17 PM

Have you tried cleaning out the IACV?

 

Something simple which is worth at least ruling out.



#11 Adictions

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Posted 20 March 2015 - 06:41 PM

How would I clean it?

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#12 duncanm

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Posted 20 March 2015 - 07:32 PM

http://www.subyclub....-iacv-cleaning/

 

take note of the 'clean without removing' comment -- give it a go with some UEC.



#13 crjohnson

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Posted 21 March 2015 - 05:20 PM

Any idea if anyone has tried putting in a different ecu? Maybe from a liberty or forester? I have an ecu from a my03 foz, might look into installing it, though there are a few differences that I can think of (exhaust recirc valve, 2nd sensor for the cat)..



#14 duncanm

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Posted 21 March 2015 - 06:49 PM

Any idea if anyone has tried putting in a different ecu? Maybe from a liberty or forester? I have an ecu from a my03 foz, might look into installing it, though there are a few differences that I can think of (exhaust recirc valve, 2nd sensor for the cat)..

err - why?



#15 Beckers

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Posted 21 March 2015 - 07:11 PM

Just wondering if ya have the A/C on ??

 

My outback is rough as fork in the lower gears when using the A/C.

On decell it will have something to do with the cutting off fuel to improve emissions, once you take the foot off the pedal.



#16 Barbbachello

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Posted 21 March 2015 - 07:18 PM

err - why?

+1


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#17 Adictions

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Posted 21 March 2015 - 07:19 PM

it is better with the ac of but still there might give UEC a go soon


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#18 El_Freddo

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Posted 21 March 2015 - 10:06 PM

My mate (aka Venom on several forums, just not here :() has toyed with the idea of a full aftermarket ECU.  His conversion is using a factory ECU with a piggy backed TCU to tell the ECU that that non existent auto is happy all the time.

He's cleaned the IACV - including out bush on one trip he was that frustrated!

 

I don't think swapping factory ECUs will be beneficial, just a PITA!

I'll be keen to learn if someone works out a long term solution for this!

Cheers

Bennie


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#19 crjohnson

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Posted 22 March 2015 - 09:57 PM

After reading through El freddos link, the guy talked about the IAC valve and how it acts. Thought that since you can't change its settings maybe try a diff ecu??

But what he mentions about the restrictor plug could be worth a shot at helping the jerking (not necessarily solving it though).
Still more new bushes to try though I think!

#20 Adictions

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Posted 25 April 2015 - 10:44 AM

Im gonna give uec a go today and give it an oil change. Any oil recommendations, it burns nothing so im thinking 5w30 mineral.

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