01 Chevy Cavalier 2.2 that bucks

[lilpenny]

Hello everyone I am brand new to the forum. I have a 2001 Chevy Cavalier 2.2 that starts up a little slower than usual. After driving around a couple of blocks the car begins to buck really hard and then stalls out. My mechanic has changed the batter, spark plugs and wires, crank sensor, air sensor, temperature sensor, both coils, control moduler and both coils, and the fuel line. When it is cold the car bucks the most and then I hear a pop and the car stalls out. The emissions light is on and the code said Catalyst System Efficiency Below Threshold (Bank 1). My mechanic said the converter is not plugged and is fine. Please help!!

[dave02cav]

Coil pack could be bad? or maybe too much oil in air box around TB? is TB coated with oil?

[Spyder3K]

I had the same OBD code on my 2.4L but it was the cat that was bad. I'm thinking it could be a poor O2 sensor. At least, that's what my dealership said, if it wasn't my cat (but we knew it was). Are there any other codes or problems that are occuring?

[Helmuth48]

There are sensors on the engine that adjust the air/fuel mix for a cold or hot engine. "When it is cold, it bucks the most" ....this tells me, the timing/air-fuel mixture maybe off...

1. Check the ECT sensor ?? Not say it is it or sure....but I have seen it cause the same effect.
2. EGR valve ???
3. IAC valve ?

Good Luck...JzJzz