Hi. I have a 2002 cavalier ls with the 2.2 ecotec. I recently replaced the motor with a 03 sunfire ecotec. The car runs rough and pops and sputters when first started. Doesn't matter if the motor is warm or cold. After about a mile down the road it smooths out and runs good. The check engine light is on with a misfire code and bank 1 rich. I changed plugs, swithched the icm and coils. Tried the fuel rails and injectors from both motors. nothing helps. Any ides?

 

could be a lot of things. the car uses speed/density fuel metering. Anything that would drop the map reading would cause the system to go rich..ie intake manifold leak, vac leak.

post all the dtc that have set and we can work out where to start.

 

I found no leaks any where. I sprayed every where with some starting fluid and there was no leaks