Random shuddering in Park when AC is on - '13 LC

[zgstar]

Hey All!
I was in search of a reliable SUV for my cross-country move and wanted something I would keep for longer than 3 years, so I bought a Toyota Certified Pre-Owned '13 LC in Vegas and drove it 2500 miles cross-country within the first week. It was an uneventful road trip, but it did allow me plenty of seat time to compile a list of everything wrong with the car that I wanted Toyota Certified to fix. So far, the Toyota dealer has replaced the LH KDSS control unit. I've come to ih8mud.com to humbly ask for your advice on the following issue that the dealer is having a really hard time figuring out:

When my '13 is warmed up, in Park, and the AC is on, I feel singular random shudder-like vibrations in the idle every 1 or 2 seconds. This only happens when in Park. When at a stop light in Drive with my foot on the brake and the AC on, the idle is completely smooth. When in Park with the AC *off* the idle is also completely smooth. The Toyota dealer cleaned the throttle body and did some kind of ECU update in an attempt to fix the issue but the issue is still there. The vibrations are random and noticeable enough that if you are in Park and the AC is on, you wouldn't be able to take a nap in the driver's seat.

What could this be?

Cheers and Thanks In Advance!
Bobby

 

[Docboy]

Has the dealership thought of replacing the AC compressor?

 

[zgstar]

Has the dealership thought of replacing the AC compressor?

It hasn't been mentioned. The AC blows cold, so it might be a difficult proposition convince Toyota to replace the compressor? I'll ask though.

 

[LBridges]

I have some serious doubts the following will help but...

Many years ago saw this problem with a broken engine mount (in a Chevy IIRC). When in drive the engine loaded the broken side and so no problem. If by some chance my remembrance has value, the diagnostic would be to see if the problem exists in reverse when the engine is not loading the engine mount. The shuddering would occur in conjunction with the idle going up/down as the AC kicks on/off.

About idle...

As my 200 is so new, haven't looked into engine systems much, but does the engine idle up properly when in both park and drive (IAC valve - if the 200 uses one)?

 

[zgstar]

I just discovered something. When I turn *off* the AC and use the gas pedal to slightly increase the RPMs from 700 (Idle RPM in Park with AC *off*) to 750 (Idle RPM in Park with AC *on*) the car vibrates! So, it's not the AC system at all. It just so happens that when the AC is on in Park the RPMs hit some vibration sweet spot (750RPM). I remember reading something about this resident frequency in another tech thread? Is there any way that this 750RPM-only vibration could be symptomatic of engine mounts?

 

[asr1]

I get something similar but at around 1000-1250 revs while in park - and 1250-2000 revs when cruising at different speeds. Previously thought it was drivetrain related but feels like something associated with the engine. Did you ever discover the source?