OK, I have a 1988 Bonneville SE with 188,000 miles on it. Just replaced the O2 sensor, spark plugs, did an oil change, replaced the air filter and then took the car through emissions after driving the car about 10 miles. It failed on the CO emissions at idle. I had a Bosch O2 sensor and replaced it with a Nippon Denso? sensor. Hopefully they both do the job. I had for results:

HC cruise limit 150 cruise emissions 68, PASS

HC idle limit 220 idle emissions 220 PASS

CO cruise limit 1 cruise emissions 0.24 PASS

CO idle limit 1.2 idle emissions 4.36 FAIL

What else can I do??? Fuel injection cleaner??? Make sure the car is really up to temperature before trying again???? Thanks for any help. Gary

Did you replace the O2 sensor after the emissions failed or before?

I replaced all those items the same day just before I took it through emissions. But I have an update. Had the wife drive the car for about a half hour, over 20 miles, and then take it in. It passed with flying colors. It has always been a cold blooded beast, I just didn't have it up to temperature I guess. Just can't figure out why it heats up so slowly. Open thermostat???

That would certainly do it. Might be time to flush the cooling system and replace the T-Stat. It'* pretty cheap maintenance!

Yeah, its probably a job I will do this summer. I have a spare bottle of Prestone radiator flush sitting in the garage. I'm just scared the fitting will break on the bottom of the radiator when I try to open it. I guess I could just take the lower hose off instead though. I still have a battery drain somewhere that I cannot find too. I have to disconnect the battery every few days so the battery doesn't drain down too much. I've pulled the fuses and tried to locate the cause but nothing seems to show up. Sometimes I can leave the battery hooked up for a month or sometimes just a few days. I did put in an aftermarket radio 2 years ago and it was a pretty smug fit. I will pull it to see if any of the wires are pinched. Thanks for the help.