Vibration at idle
 

Mark IV all-stock owner ('98), auto, have significant vibration at idle, worse at stop with foot on brake, goes away @~ 1100 RPM and otherwise engine purrs like a kitten (ok, maybe a mean one). Been to 3 different mechanics (incl Toyota dealership) and no one can fix it. FYI- I'm not a sophisticated car guy, but that's probably obvious!

1) TT or N/A?

2) Without being there in-person to troubleshoot, I'd suggest one of the likely culprits is a misfire...possibly due to an ignition issue. How old are your sparkplugs? Do you know what they're made of (copper, platinum, iridium, etc.)? How long since your last tune-up (and plug change)? How many miles on the car (and therefore the ignition system, coil(s), ignitor, etc.)?

3) Get/borrow/use a compression tester and post (or PM) the individual results for each cylinder.
http://www.mkiv.com/manual/manualtt/...eck/index.html

Thansk for the comments
 

No, not misfire. Has been vibrating for more than 3 years now and have had it serviced regularly incl tuneups/spark plugs etc. 154K miles now.
Don't even know what TT or N/A means (I said I was no car guy). I can have compression checked. I had one mechanic this week suggest drive shaft bearings (?) which is what led me to a forum for other opinions before I blow $ on that possible fix. One mechanic replaced harmonic balancer- no resolution to problem. So bad sometimes I have to shift into neutral at stops because it will drive my ears crazy.
Damn... I love my Supra but it's gonna vibrate itself to death.

TT = Twin Turbo
N/A = Normally Aspirated (non-turbo)

If it vibrates at idle (while parked), then it is NOT your driveshaft bearings.

Let me know the results of the compression test.

TT, N/A LMAO DUH! It's N/A. Will do on the compression test. Thanks again. -J

Anytime. Just curious - any modifications (eg. nitrous), running non-premium fuel (I believe the n/a still requires premium fuel, right?), or a history of hard driving (eg. drag racing or roadracing)?

Never any racing, all original- no modifications, mostly premium but occasionally mid-grade.

Are you the original owner?

vibration at idle
 

Hi! interesting point made about shifting into neutral at stops -does the vibration stop then? or is reduced ? , if so , have you checked the fluid level in your transmission? , you did say it was an automatic , , the flywheel / torque converter may be out of balance and the fluid is re-distributed as the engine speeds up and vibration reduces ,whatever is causing the low speed vibration is moving at speed and the centre of rotation is restored ( vibration removed ) , an odd point of interest but feasable if all other engine related points are eliminated .Question? have you lost a tooth on your starter ring gear on your flywheel/ the fluid may be compensating for the out of balance ?.

2nd owner- bought it in 2000 w/ ~ 20K miles.
Yes, vibration reduces substantially when I shift to neutral. Have never checked transmission fluid though I would have expected that mechanics have. "Tooth on starter ring gear on flywheel"... all Greek to me! I guess I can suggest that to a mechanic?
It occurs to me that sometimes vibration seems to worsen when I go from low gas tank level to a fill-up. Then again maybe I'm dreaming.