Hi Everyone,
I have a 1985 Z28 Camaro with TPI 305. It has the edelbrock TES headers and Y-pipe then I got a straight through glasspack in place of were the cat would go, then mandrel 3" under the axle out to the bumper. The A.I.R system has also been taken out. I also have a 160 thermostat.
The other day when I was driving I noticed while watching the scanner the computer is only in closed loop when the engine is under load. For example I was going down the road with engine at operating temp at about 65 MPH and the computer was in open loop but when I just barely increased the throttle to speed up it went into closed loop. then when went back to constant throttle position it went back to open loop. Is this normal? Or is the O2 sensor only getting hot enough when the engine is under load? Or is the O2 sensor faulty. It runs great by the way.
Thanks.

 

Problem?
No, what you are seeing sounds like lean cruise or "Highway Mode".
The ECM drops active control via BLM, for pre-determined & separate AFR.

 

Oh its going into highway mode?
Thanks for the info!