1981 here with all parts on and working. I am getting a Code 13 on the ECM check which is the Oxygen Sensor Circuit. The check engine light will come on for anywhere to 5 secs to 2 minutes and go off, does not lock in and stay lite. Pull codes and 13 comes up. Check engine light has come on for a while when sitting at red light as well as when cruising down highway at 55mph.

Is there a trick to checking out the system to see if it is the sensor itself or if it is too lean or rich at times?

I have all parts on the car, everything works and the car is as close to factory as I can keep her so no modifications done. It has a 350 GM crate motor, 195HP installed last summer and I am running 87 octane gas most of the time since timing is still set to factory spec and have no spark knock or other low octane tale tell signs. Also Q-jet carb was re-manufactured last winter by All American Carbs and have had no problems out of it since installing.

Was getting the Code 13 before engine swap and carb work done, just maybe not as much as I am now. On 15 miles run this morning in cool temps the light lite up 3 times. Does it whether in cool or hot weather.

Thanks in advance for thoughts or comments.

|UPDATED|6/2/2012 10:34:35 AM (AZT)|/UPDATED|

Sensor could be getting "lazy" causing the Check Engine light to trip.

The only way you can tell if the O2 is getting slow or lazy is with a OBD I scan tool w/ live data streaming. I still have one of those antique scanners with the "GM" cartridge buried in my tool box. lol.

If the sensor is original or there is over 30,000 mile on it I would just replace it. I remember that Bosch used to recommend replacing the O2 whenever you did a tune up.