03 highlander vibration in "d"

[fartunder]

I have an 03 Highlander Limited with 112K on the V6-had it 1 yr. In D when stopped it vibrates when warm from a little to alot-worse with AC on like it could actually stall but never does. Spent hundreds with private mech cleaning throttle body, check'd and cleared codes with no change. He jacked up on the engine while it was running to prove it was the motor mount(s) and it did seem to reduce the vibration. He says the front mount is oil filled but not leaking so don't worry about it till it does. Recently figured out that it mostly goes away if I turn the steering wheel just until it resists but dosen't turn the wheels. Could it be a PS pump going out? That's all I've got. Wish I could figure this out-it drives me nuts.

[avconsult]

Well, it may be the radiator side motor mount--it is oil filled but uses engine vacuum to generate counter pulses, and if that stops working there will be noticeable vibration. There is a procedure in the service manual for testing it.

Also heard of Toyota radiator hoses that have hardened which have contributed to some vibration.

If any of the other mounts have surface or deeper cracks, they need may replacing as well--they get hard over time with exposure to salt, ozone...

[avconsult]

By the way, when you turn the steering wheel a bit it kicks the idle up by about 100 RPM, which reduces the vibration quite a lot.

My '02 V6 vibrates like yours-- I just haven't bothered to change out the engine mount yet. If I could figure out how to tell the ECU to raise the base idle by 100, I'd blow off the engine mount.

[LifeTech]

Why would yu want to alter the RPM to "out of specs" just to compensate for a poor engine mount?

These engines are not from the 50's and 60's.
The HL Idle is preset and ECM controlled.

The front engine mount on my 06 V6 3.3L HL is electrically controlled. It has wiring to it. Check yours if it has it also. Check the connectors for continuity.

LT

[avconsult]

Yeah, I am quite aware the ECU controls idle, and more than occasionally manufacturer's issue bulletins to change that base setting up or down. Sometimes to compensate for gradually hardening rubber components on engine mounts, exhaust hangers, radiator hoses that are not technically "failed", but change the compliance and natural resonance of the system. Sometimes to provide slightly better A/C performance in hot climates, etc.

The vacuum controlled mount (maybe the same on your '06) uses a pulse width modulated solenoid that triggers vacuum to the mount bellow in sync with engine firing in order to created a phsysical pulse in the opposite direction as the engine and partially cancel vibration. It's a bit involved to troubleshoot, but the service manual is detailed.