Idle vibration and then smoothness

[hobosapien]

Hi, I have a 2004 4runner v8 Limited.

When my 4runner is idling, it will switch back and forth between an ultra smooth idle where I can't feel the engine operating (normal), and then a somewhat rough idle, almost as if it was running harder for the AC compressor. Granted, it does it without the AC on as well. It goes back and forth in a cycle it seems.

Any ideas on what could be causing this?

 

[harryJ]

Funny thing, I recently got the same exact issue on my V8. The vibration is only in drive, super smooth in park. Let me know if you figure out the issue.

 

[EdmundGTP]

It's the AC compressor.. Even if your HVAC controls show the AC as being off, the HVAC controller will kick on the AC compressor intermittently to act as a dehumidifier depending on what your climate control/defrost settings are. I've found that if you don't want the AC compressor kicking on, then do not use the vent setting that blows air up at the windshield. Set it to use the direct, or foot-well ducts.