So I've noticed on my last couple of trips to and from NYC, the car is running beautifully until I hit heavy traffic.

It seems to me that the front 02 sensor is going whacky when the Y pipe gets hotter due to the heat produced by the stop and go traffic. I thought it was the coils and they've been replaced.

Anyone else experience this? I doubt my cat is bad since I just replaced it last fall with a Warpspeed.

 

I think that you may be onto something! I'm having the same symptoms as you, and I've recently had a recurring check engine light for 0308 - right bank oxygen sensor. Didn't know that a bad O2 sensor could cause engine studder. It's very slight, but it's definitely there idling in traffic when the car is fully warm and been driven a while.

Needless to say, I'll be replacing this weekend along with a shorted air mix motor, front and rear brakes, front rotors, a bad left wheel bearing, hood struts, oil change, trans fluid change, side engine mount, sway bar end links, evap canister valve 0705 / 0903, and anything else that I find. Gotta love springtime maintenance!

 

Well, I've come to this conclusion based on everything else that has been done. I can accelerate hard and get no studder at all. I'm waiting for the new 02 sensor to show up so I can install it before my next trip to NYC which is in a couple of weeks. I changed them all when the car had around 250k miles on it so I'm figuring it's time to change the front one again. I'm at 380k now.