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.

vibrating at idle
 

Hi again ! the flywheel has a ring of teeth around it fanning outwards ( like daisy petals ) this is the means that the engine is turned by the starter motor to start the engine . If one is missing or chipped ( part of the tooth is missing ) , the flywheel is out of balance by one tooth / chip - by diameter of the flywheel and the crankshaft will vibrate , this MAY be the cause , and the fluid in the torque converter may be compensating by moving at greater speed to offset the imbalance , it's only a theory but may also be worth checking by getting underneath the car and removing the plate at the rear of the engine / transmission and turning the crank 360 degrees to check for a missing tooth / chipped tooth .

Has it been vibrating like this since you bought it w/20K miles? If not, when did the vibration start (and did it follow any maintenance or unusual event you can recall)?

No the vibration started about 3 years ago and I had several shops try to diagnose the problem with no luck. Nothing changed that I could point toward as a cause.

Again, please post up the results of the compression test. At this point, that seems to be the most appropriate next troubleshooting step.

It could be a clogged injector as well. Or maybe a bad one. In reality it could be anything. But the moderator is right. without test results of com, tests, injector sets and using all the diagnosis tools available it is impossible to diagnose your car. If you told us what test were performed by the mechanics that have already looked at the car. That would be helpful. Very helpful.