jzwu

OP, what's your idle speed/rpm?

I noticed on my 2002 with 56k miles sometimes the car vibrates a little at idle and the engine rpm is just over 500 rpm. But it usually picks up the idle speed a bit and the vibration abates.

Guess it is the electronic engine control adjusting the idle rpm to be as low as possible to be fuel efficient.

scdroptop

iTrader: (1)

If you are out of warranty, I would certainly start with the least expensive first: Air filter, throttle body cleaning and fuel treatment. Make sure you are using premium.

Next, if no luck...I'd consider plugs if they were not done. You will need anyway.

If still no luck, I'd move to the motor mounts and perhaps trans mounts. Good advice by LiquidSC to shop Toyota dealers vs Lexus dealers...they do compete for Toy/Lex business since they share many of the exact same parts. Also search internet for Lexus service coupons or Toyota service coupons for any services. Save all you can! Paying for these out of pocket will be pretty steep. Mine were a lot more than Bob's...I want to say closer to $1k with labor and everything.

I've had both engine and trans mounts replaced on both my SC's. Slight shaking was evident on both, at stops with the A/C off more at lower RPM's and seemed to smooth out with the A/C on. I actually still have a little shake on my 2005 CPO and plan on taking it in to have it looked at again. I've cleaned throttle body...may be time for plugs?

jasone36

Thanks for the detailed response, scdroptop. My idle is around 600 RPM when engine is warm, which I assume is normal.

I wonder if there is any way to tell when the spark plugs were last changed (the online records do not show spark plugs explicitly), and the on board diagnostics (OBDII) sensor is not throwing any error codes.

VVTiBob

Does it appear the previous owners took the car into a dealership for routine maintenance? If so, then they probably followed the standard maintenance schedule of 120K for plugs. If not, then the only way to tell is an inspection.
As for mine, it was only one mount unlike SCDROPTOP's showing premature wear so my warranty only covered it. That one replacement completely resolved my vibration issues.

jasone36

Looking at the dealer records, it very much appears that the original owner (who owned it for almost 10 years) did take it to the dealership for routine maintenance, at least up until around 100K miles.

The final service record from the original owner indicates "100K+ mile schedule service performed", which was 1.5 years ago. Prior to that, a 95K service was performed, 90K service, 85K service, 75K service, 45K service, 35K service, 10K service, 5K service, and a bunch of other services in between which do not have a mileage tag in the description.

VVTiBob

Major service occurs at 60, 90 and 120K .... You skipped over some of those in previous post. If you have the owners' manual check it out. But it sound like you need the 120K + service.

robertrios

iTrader: (11)

my car has a vibration that is very very slight it cant really be noticed unless Ive been driving my Is250, with the top down ill notice my sun visors vibrate slightly and then when I see that and Im aware ill notice that its the car vibrating in general. The idle is fine and the dealer found nothing wrong and said thats because its a V8 engine. Again...not really a noticable or bad vibration just something is there versus the Is250 where there is nothing at all.

jasone36

I have made some additional observations about the shaking in my SC430.

When the car is in Park with the Parking Brake enabled (engine running) the car does not shake. As soon as I put the car in Drive I get the shaking. If I enable the parking brake while the car in Drive and hold the brake down I still get the shaking, thus I can conclude the parking brake makes no difference. But it does make a difference if the car is in Park (no shake) versus in drive (shake).

I asked a dealer they also said it could be a "vacuum leak", in addition to the possibility of motor mounts and possible spark plugs (?). Of course, they want $120 diagnostics fee to "thoroughly test drive the car", which I can't seem to justify, this I turn to the real experts, you guys...

Thanks!

Jabberwock

Couple of suggestions in case it is not your motor mounts. First thoroughly clean throttle body, use white cotton rags and TB cleaner spray, then clean MAF with spray designed for MAF or electronics parts cleaner, then make sure air filter is clean, then run a couple of cans of Techron fuel system cleaner concentrate (avail at auto parts store) thru two consecutive tanks of gas. Also inspect vacuum and other hoses in and around the air intake to make sure none are cracked, broken or disconnected. Keeping the air and fuel systems spotless typically produces a nice smooth idle.

scdroptop

iTrader: (1)

mmmmmmm

Last time you changed your serpentine belt? How about changed the rear diff and tranny fluids? Some potentially overlooked regular maint items that get neglected sometimes (not the belt).

Could be rear diff....

fpatton

My '03 with 39k on it (yes, really) does exactly the same thing, and it has been immaculately maintained and I know the entire service history.

My thinking is that it's an engine management issue, i.e., software. I think what's happening is that the ECU idle control is optimized for the A/C compressor on, because they assume you'll have no reason to turn it off. (In cool weather, it serves to dehumidify the air.) When you do turn it off, it doesn't make the appropriate adjustment, and the result is a slightly rough idle.

My two cents.

Fred

jasone36

fpatton, your explanation is exactly what I hope is going on... if that is the case I'd be very happy.

I have decided to take no action for now, as I'm hoping I will get used to the slight shacking. Half the time it isn't even noticeable at all.

jasone36

To follow up on this thread, I replaced the very dirty engine air filter with a Purol A35449 air filter from Advance Auto Parts ($29) and the shaking decreased VERY MUCH. Now the shacking is barely noticeable.

As many in this thread recommended, I will also change the spark plugs, I will use Iridium (3297) spark plugs from Advance Auto Parts ($72 for a set of eight) to see if the remaining subtle shacking will go away.

dnguyen

Hello Jasone36,

Have you changed spark plugs yet? If you did, can you please update status. I just purchased 2004 with 34k miles, i got very similar problem with your car. In my case, I got the car from this seller. He kept that car flawsly clean, service records up to date.

Thank you,,

jasone36

dnguyen, I did change the spark plugs for the Iridium (3297) spark plugs and it helped a lot. However, a very slight shaking can still be felt, but seemingly much less than before the spark plug change. Other folks have posted that they think it has to do with the car software and may be considered 'normal' on a 2002-era car. Yours is a 2004 so I'm not sure.

Out of curiousty, how much did you pay for the car?