Car vibrates at idle.

which engine.??? never post lacking engine ,here is why.
1.3 L G13B I4
1.5 L G15A I4
1.6 L G16B I4
1.8 L J18A I4
1.8 L BP-ZE I4
1.9 L XUD9 diesel I4

Ill answer in the generic and for GAS engines. only.
that is illegal RPM, the ECU regulates it to 800 all the time
that means the ECU can not regulate the RPM now, for many reasons.
and sure it vibrates too low, that is normal for all 4cylinders to do that.
no bad engine mounts never lower RPM to 600, ever.
they dont control idle speed at all.
the #1 reason for most cars to idle too low are:
1: EGR leaks, (clean it)
2: ISC stuck closed (electric idle speed acututor dirty) clean it.
3: gross misfiring , caused by bad spark or bad fuel mix.
4: low compression on 1 or more cylinders (real low) Do compression test at WOT. throttle.

Wow thats a bunch of miles for only 9 yrs.
I would want to know if it is something related to the engine or transmission, or the wheels and suspension.
Does it happen in all gears, and at any road speed ? Can you rev up the engine and make the vibration, or does the car have to be moving ?

oh,, we'll need some more information to be able to help, The thing is you didnt specify what vibrates for example when you start and you have vibrations while idiling, while in drive and the engine kicks back rough when changing gears more than likely its and engine mount thats bad. if its vibrating while idling its the fuel rpm ration (idling screw that needs adjusted or the MAP or air sensor if its fuel injected).. If its vibrating while the ac is turned on, check the ac step-up solenoid (the switch that increases the idling speed to match the ac's needed power.) we'll love to help or point you in the right direction but we'll need some more information. Describe whats happening for us , because we cant be there in person to actually experience it our selves. If you have a vid of the engine while vibrating etc all of that will be beneficial.

There re few possibilities that can cause no idle issues.To troubleshoot the issue help links are provided below.Click the link below:---
Idle Problem? http://whatisbyme.blogspot.in/2012/05/2001toyota-corolla-idle-problem.html
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Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------
Stumbling and stalling at idle after engine rebuild? http://schematicsdiagram.blogspot.in/2012/03/stumbling-and-stalling-at-idle-after.html

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Cooling fan Shuts OFF and Idle Drops? http://howtobyme.blogspot.in/2012/05/toyota-celica-cooling-fan-shuts-off-and.html

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Rough Idle and Vibration? http://whatisbyme.blogspot.in/2012/05/2006-ford-f150-rough-idle-and-vibration.html

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Steering Wheel Vibrates at Idle? http://whatisbyme.blogspot.in/2012/05/1993-toyota-corolla-steering-wheel.html

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Runs Fine But Idle Is Low? http://whatisbyme.blogspot.in/2012/05/2004-toyota-highlander-runs-fine-but.html

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Vehicle Will not hold Idle? http://whatisbyme.blogspot.in/2012/05/2003-lexus-es300-vehicle-will-not-hold.html

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Engine Idles Rough and Dies? http://whatisbyme.blogspot.in/2012/05/1994-lexus-es300-engine-idles-rough-and.html

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This will help.
Thanks.

Get the Idle air control valve checked inspected.Also its suggested to get more troubleshooting done.For more troubleshooting,click the help,links below:---Idle Problem? http://whatisbyme.blogspot.in/2012/05/2001toyota-corolla-idle-problem.html
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Runs Fine But Idle Is Low? http://whatisbyme.blogspot.in/2012/05/2004-toyota-highlander-runs-fine-but.html
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Vehicle Will not hold Idle? http://whatisbyme.blogspot.in/2012/05/2003-lexus-es300-vehicle-will-not-hold.html
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Erratic Idle and Intermittent engine stalling? http://technoanswers.blogspot.in/2012/04/1997-toyota-camry-erratic-idle-and.html
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Stumbling and stalling at idle after engine rebuild? http://schematicsdiagram.blogspot.in/2012/03/stumbling-and-stalling-at-idle-after.html
---------Cooling fan Shuts OFF and Idle Drops? http://howtobyme.blogspot.in/2012/05/toyota-celica-cooling-fan-shuts-off-and.html
-------Rough Idle and Vibration? http://whatisbyme.blogspot.in/2012/05/2006-ford-f150-rough-idle-and-vibration.html
--------Steering Wheel Vibrates at Idle? http://whatisbyme.blogspot.in/2012/05/1993-toyota-corolla-steering-wheel.html
--------This will help.Thanks.

This is a rough idle, what is causing it is a big open question, you will need a tech to evaluate the problem. It could be just worn out engine mounts or a slow idle issue or many other things.

That mechanic wasn't lying. I currently own three of them and I know a lot of people that own them and they all have a rough idle. The engines are internally balanced and they don't have dampeners, so you get the engine vibration transferred to the car and that is what you are feeling.

check engine and gear box mountings

Check to make sure both headlights are tight,,,when it rattles at idle go feel the headlight and hold it and see if the noise and vibration goes away,sometimes the headlight has too much clearance and causes a massive vibration,,if thats not it try...loosening all the motor mounts and rock the car back and forth and them retighten them,it reseetles the mounts and sometimes fixes the issue,,also check the lower engine and trans mounts for wear.

IF GEAR SHIFT SHAKES THEN THE TRANSMISSION MOUNTS COULD BE BAD. HOPE THIS HELPS. GOOD LUCK