This morning I find the car has lumpy idle after it has been warmed up.
What gives? Temp was around 27F.

Here are couple of shots....One with car in N. No issues there.
When in 'D', however the idle is very lumpy. The whole cabin was vibrating.

What could this be?

 

I dont know what you mean by lumpy. But if its your idle not being stable in Drive taking pictures of it is not going to show us what you mean. You can record it. Cause unless im something your first picture looks just like your 2nd one.

 

First time like this? Probably the oil transmission is still cold.

 

I had this too, it was about -23C and my engine was shaking. like actually shaking. But it settled when it warmed up and hasn't happened since. I'm not sure what that means if it was happening while it was warm though. Might want to take it to dealer if you're on powertrain.

 

I thought that's pretty common since you were close to motor oil freezing point.

http://wiki.answers.com/Q/What_is_th...t_of_motor_oil

 

Mine does that too when its really cold I think its because the trans fluid isn't warmed yet.

 

there is a diff of 200 between the two pictures. Of course I cannot take pictures of the vibration, so this was the best I could provide.

 

yup. This is after driving 25 miles.

 

It's the cold weather and your oil warming up. I don't have that problem any more ever since I switched to 0W-30.

 

The engine is fully warm, and I am using 5w30 Mobil1 full synthetic.

 

I've had the engine do the same after swapping intake filters and unplugging the battery. Maybe you could unplug the battery. It's done it on two occations that had probable causes. Near freezing weather & intake filter swap. Maybe I touched the MAF sensor.

 

I figured it out....damn EPA software issue.

This morning it was freezing cold so I let the car Idle for about 15 minutes while I had my breakfast before going off to work. Apparently, as you idle more, the engine trims the fuel and causes idle to drop (from my observations).
For example, when I come to a stop gently, the idle stays at 1000, ready to take off if needed. but after about 5 seconds, the rpm drops a a little, to about 750, and then some more to 650.
Given that this morning it was idling for about 15 minutes, the engine was idling at 550 (in D) rpm making it lumpy.
Not fun at all.

As I drove back this evening to home, I did not idle the car at all when taking off from work. The idle behaved just fine and the temp was 30F.

 

I wouldn't go as far as saying it's an EPA software issue. Several things come into play. Oil temperature, the amount of time the car had been off. Frozen condensation inside the exhaust system. Even the battery can play a role in how the car responds in the cold morning.

 

You shouldn't leave your car idle for more than 10 seconds. It's not good for your engine.

http://www.thehcf.org/antiidlingprimer.html

 

Interesting read... None of which addresses what I was taught.
Bringing an engine up to temp was important due to its construction.
As you have several materials it is constructed of, each heat up and expand at different rates.
Cast iron blocks, and aluminum heads are often a problem, as the uneven heating has been known to blow head gaskets or even crack the heads themselves.
Rapid heating is also attributed to premature metal fatigue, or warping of parts due to localized hot spots.
Also, a cold engine has massive clearances in all its critical areas (bearing journals, lash adjusters and such) that should be much tighter in tolerances before placing undo stress on them.
In all my years of mechanicing, the general rule has been to always bring the engine up to temp before placing stress on its componants.

2cents
Vince