I just purchased this car and the next day the Check Engine light comes on, but the car ran fine, idled good for a month. Autozone checked codes P0141 & P0147 which is the Right (passenger side) O2 sensor behind the CAT.

After a month, the idle got rough and gave a little problem at stoplights. I finally got a new sensor and when I went to replace it, I found the original was very loose, almost coming off, so I put some hi-temp thread anti-seize and tightened the original one down. It ran back to normal, not great, but normal idle.
I discovered that the vacuum reservoir had fallen loose and was disconnected (who knows how long). When I plug the vacum line back to the reservoir and start the car, it idles terribly and dies out. I can't even keep it running with my foot on the gas. It surges up to about 1500 rpm and down to less than 300 and swings up/down until it dies. I had to unplug the vacuum line from the plastic three ball reservoir again to be able to drive the car. I also replaced most of the vacuum lines in the front because they crumbled when I touched them. I will replace the rest tomorrow

Do I need to reset the ECU to have the ECU learn the new mixture with the reservoir plugged or is there something still wrong with vacuum system or O2 sensors? Has anyone experienced thsi before?

Any help is greatly appreciated.

 

Press down on all of your electrical connectors. Sounds just like what happened to my car when the MAF connector come loose.

 

The car had the driver's fender replaced few years ago. I think they mixed up the hoses and there should be some canister somewhere where that hose connects to and the other ones should connect to the reservoir.

I replaced vacuum hoses that disintergrated and can ran fine with that one hose unplugged. But I think it runs lean and the check engine light came back on this week.

I have to find more diagrams or pictures of what is under the fender

 

Get a Bentley manual at ecstuning.com they also sell the nice braided vac line. Replace all of your lines. You should invest in a cheapo vacuum pump at the auto store. hook it into the lines and you should hold vacuum, not forever but it shouldn't loose vac right away. You can also mist the engine with carb cleaner and see if the idle increases. if the vac lines suck in carb cleaner it will raise the idle.

You need to pull every electrical terminal clean the contacts and apply di-electric grease. Cable tie them in if they are cracked. Your Ignition coils may need to be replaced that would cause CEL also the engine mounts are liquid filled and if they are bad you will vibrate through the brake petal at lights.

Unfortunately the previous Richie rich owners of these cars don't need to wrench on them, So they don't!