Its a 2000 Sunfire 2.2L with a 100,000 miles on it. Its giving a 420 code. The cat was replaced a year ago with 85,000 on it.( the last time it gave a 420 ) I figger it shouldnt be the cat agin a year and 15,000 highway miles it should be like new. I have replaced the O2 sensors ( before and after cat ). Its had a tune up and new air filter. Its my wifes car and she says its always at a stoplight when the light comes on. She says the idle speed will drop a little bit and the light comes on. Any ideas ?
