I'm going to be replacing my stock AC Delco o2 sensor with a 3-wire heated Denso o2 sensor because of my headers.

I plan on leaving everything alone in the PROM for the most part because I realize things like from a cold start the engine/oil/& coolant requires a variable enrichment before the car can be taken from open loop to closed loop and that it also gives the CAT time to warm up. Sure I could account for this by changing the commanded AFR at those coolant temperatures but in a not so modified engine, why bother when it works just fine now.

What I am specifically wondering about if the time it takes to enter closed loop when I start the car and it's already at full operating temperature, like the gas station or some other quick stop. What are the variables I can modify to affect this?

Most important to me is the fact that people here mention that when the engine idles for a certain period of time or you are coasting down a long hill, the ECM will enter back into open loop. Also that the ECM will not switch from open to closed loop after starting until you begin driving.

How can I ensure that the ECM never reverts back to open loop unless the engine is turned off and turned back on. I'm especially interested in this because I am up for smog and they tend to let the car idle for an extended period of time while doing the visual inspection.

Thoughts?

Thanks!

 

Never experinced that the ECM goes out of closed loop after installed a heated 02.
Regarding the time it will take for the car to re-enter closed loop after a shutdown, is depended on engine coolant temp and the closed loop delay timer constants. And yes, these can be changed. But you really shouldent need to.