Cabin Vibration

[artbuc]

99 Toyota Avalon with 1MZFE V6

Have been chasing a cabin vibration for a couple years now. You feel it mostly in the steering wheel when the car is stopped in gear but not so much in neutral or park. Have replaced all mounts with OEM...no effect. The car idles beautifully and has plenty of pep. Idle is set at high end of specified range. Fuel trims are perfect (short term at 0 +/- .8 and long term +/- 3) and have no CE codes. However, if you put your hand on the intake manifold and rev the engine, when the rpms quickly drop, you can feel a pulsation almost like an out of balance shaft or restricted exhaust causing a pulsing back pressure. I do not know if this is related to or even causing the cabin vibration but I suspect it is.

Does anyone have any ideas or even a wild guess or to what is going? Thanks.

 

[mazdamonky]

Motor mounts? specifically the rear motor mount attached to the firewall if there is one.

 

[Pelican]

Originally Posted By: artbuc
99 Toyota Avalon with 1MZFE V6

Have been chasing a cabin vibration for a couple years now. You feel it mostly in the steering wheel when the car is stopped in gear but not so much in neutral or park. Have replaced all mounts with OEM...no effect. The car idles beautifully and has plenty of pep. Idle is set at high end of specified range. Fuel trims are perfect (short term at 0 +/- .8 and long term +/- 3) and have no CE codes. However, if you put your hand on the intake manifold and rev the engine, when the rpms quickly drop, you can feel a pulsation almost like an out of balance shaft or restricted exhaust causing a pulsing back pressure. I do not know if this is related to or even causing the cabin vibration but I suspect it is.
Does anyone have any ideas or even a wild guess or to what is going? Thanks.


Did you replace Motor & Transmission mounts? or only one of the two?

 

[SatinSilver]

Try some Lugegard Red in the transmission. Someone on here recently did this after changing motor mounts and a ton of other things. Also don't forget the pcv valve, cleaning throttle body, etc...

 

[artbuc]

Originally Posted By: SatinSilver
Try some Lugegard Red in the transmission. Someone on here recently did this after changing motor mounts and a ton of other things. Also don't forget the pcv valve, cleaning throttle body, etc...


Yeah, followed Oro's advice...did not make any diff.

 

[artbuc]

Originally Posted By: Pelican
Originally Posted By: artbuc
99 Toyota Avalon with 1MZFE V6

Have been chasing a cabin vibration for a couple years now. You feel it mostly in the steering wheel when the car is stopped in gear but not so much in neutral or park. Have replaced all mounts with OEM...no effect. The car idles beautifully and has plenty of pep. Idle is set at high end of specified range. Fuel trims are perfect (short term at 0 +/- .8 and long term +/- 3) and have no CE codes. However, if you put your hand on the intake manifold and rev the engine, when the rpms quickly drop, you can feel a pulsation almost like an out of balance shaft or restricted exhaust causing a pulsing back pressure. I do not know if this is related to or even causing the cabin vibration but I suspect it is.
Does anyone have any ideas or even a wild guess or to what is going? Thanks.


Did you replace Motor & Transmission mounts? or only one of the two?


Front and rear plus dogbone on top...all OEM. Transmission mount original but it looks good. Also, I jacked up transmission a little to relieve load on transmission mount which made no diff.

Any thoughts regarding the pulsation/out of balance sensation on intake manifold during rapid deceleration?