Hi everyone,

I'm wracking my brain as to what be the cause. Any guidance will be appreciated! Upon start up, the engine is sewing machine smooth. As it warms up, I feel more vibration. In gear and in Park/Neutral. Mileage and power are both excellent. NO Codes showing.

2007 4.0L V6, Sport Edition 4WD. 340,000 2nd owner. Pristine condition.

I baby this thing. I put 300,000 on a 2005 4.0L 2WD. Bought this one with 212,000 miles, one owner.

Mobi1 filter and oil. Have run both Lucas and Berryman injector cleaner through full tanks of gas. I regularly use the Lucas Ethanol treatment to mitigate negative effects of ethanol in gas.

In chasing this vibration, I have:
Removed and cleaned the throttle body assembly.
Replaced spark plugs with Denso Long Life Iridiums.
Changed PCV valve.
Checked every vaccum hose.
Cleaned MAF sensor.
Checked integrity of radiator cooling fan. All OK.

I'm wondering if it may be motor mounts (Toyota calls them insulators)?

Any ideas on where to look? The fact that the vibration starts after the engine is at operating temp is a clue.

Thank you and I will be sure to follow up once I identify the cause..

With the high mileage on your ride, the vibes might be coming from the drivetrain, like the torque converter or the transmission. Check out the transmission mounts too - worn ones can make things shaky, especially when you're putting some load on.

Take a good look at the exhaust system too. Any issues there, like misalignment or worn-out parts, could be causing those extra vibrations, especially when the engine is warming up.

And since your vehicle has been around for a while, it might be a good idea to do a compression test on the engine. That can give you the lowdown on any internal issues that might be causing the vibrations.