So i have a CODE 13 when i flash the codes...
it takes about 10-15 mins for this code to come on....

my car runs normal.. idles proper etc....

once the code comes on... my power decreases and my idling drops....
when at a stop light it'll drop to 500rpm and sometimes feels like it wants to just drop on me but "catches" and picks itself up for a few secs then goes back to 500rpm...

i have already replaced the o2 sensor...

any other suggestions?

throttle position sensor sticking?
fuel filter?
poor connection?


i'm at a lose here :/

 

I am having the same problem. im glad i read this, i was just about to change my o2 sensor. i am also having serious bad gas mileage. the difference is i have a 1991 firebird v6. it has been a problem since i got the car 4 months ago but i cant seem to figure it out.

 

Sounds like the sensor is all done. They don't last forever. I've had them go bad in 30,000 miles.

 

Do the diagnostics from the FSM

http://www.chevythunder.com/o2_sensor_diagnostics.htm