Maybe some of you have heard this before so hopefully you can give me a hand. My check engine light would come on depending on how the car was driven. From what I could recall it started when you would speed up then let off the gas or top a hill and let of the gas to coast. It took me a while to put the blinking light in the ECU to the code in the book but it was flashing a single light about every 7 seconds so that told me it was the 02 sensor. Got a new one and it ran for about a week without the dash light coming on. the light would go off after the engine was turned off but the blinking red under the floor mat would continue when the key was on. the light came back after about a week but we needed to have the smog done so we rested the ECU and had it done. well it didnt pass but we needed to find out where the problem was and thought the test would tell us something. Anyway it was high on the HC PPM and the CO was also high. there was no test for NOx . the tech said it was most likely up stream from the o2 sensor on the intake side as it was running very rich and that was the reason that the results were so high he rattled off several things that it could be including some of the sensors arould the intake. He never mentioned the Cat Convertor . could use some guidance, have done lots of work on the older motors before computers but Im a little buffaloed with this. hope someone has some insight. Thanks Mark