Hi...have not been here for many years. Hope you don't mind me asking a question about my 99 Avalon because not much action on the Avalon forum.
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. Fuel trims are perfect (short term at 0 +/- .8 and long term +/- 3) and have no CEL 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.