Background info - Stock 305 with Heddman headers and midpipe, installed Michigan Motorsports TBI heated O2 sensor adaptor. Power is coming from the additional ignition-on ports on the fuse block and it is grounded on the fender. Drove the car for about a month then the power wire came loose under the pedal and was crushed by the clutch and shorted. I replaced the wire, and started experiencing bogging under load when in closed loop. I tried replacing the entire adaptor and O2 sensor with the same model as well as another brand to no avail. I borrowed my friends diagnostic tool and took a ride to see that the brand new O2 sensor was reading under 100mV when I am experiencing the bogging. These sensors are supposed to operate within 100mV and 900mV. I have attached a pic of the diagnostic tool when the car is bogging. I'm not sure where to go from here, can anyone give me any advice?

 

O2 sensor is showing WAY lean.

Question is whether this is real, or false information.

Short- and long-term fuel trim numbers are both neutral (128) so overall the computer thinks the fuel trim is good under this driving condition.

I don't understand why you need to add a heated O2 sensor, when GM thinks the non-heated unit is going to work just fine. Where does Heddman put the O2 bung?

 

The headers did not come with a bung, I welded it on the collector on the driver side header. Also would like to add that the car drives fine when not in closed loop, full power and no bogging.

 

Still looking for some help here guys if anyone knows anything on this.

 

I would suspect that there is a fuel delivery issue.

RBob.