HELP - Today for the first time my engine idled very unevenly as if it was only using half the cylinders. It happened 3 times on a 40 mile round trip. Each time while sat stationary in a queue of traffic in gear. Putting it out of auto and into neutral made no difference. Each time when I depressed the accelerator the uneven idle went away and did not return until later in the journey despite idling in traffic many times. The engine has never stalled and no obd codes were thrown. It sounds and feels like not all the cylinders are firing.
What would cause this, perhaps CPS sensor on the way out?
2006 auto with 57k miles

 

Mine does a similar thing, sometimes the RPMs dip to ~200 and the dash dims and almost seems like its about to stall, but never has so far. Kinda shudders and they bounce back up to ~500.

 

Sounds similar but dash does not dim and revs are maintained although very lumpy as if only firing on 4 cylinders. Will stay like this until you increase throttle by either pulling away in gear or out of gear using throttle. Does not return for quite a while sometimes not at al that day, very random but when it does it's always at idle.

On MB forum some have sugested new ignition leads or throttle pedal sensor???

 

Had this same issue, and originally suspected the things listed below in this thread. Then I realized the air box wasn't sitting correctly on top of the throttle body. Worth a check, just takes a couple seconds.