Stumbling on Cold Starts

[Wgesnerjr]

I understand the ECU doesn't adjust Air Fuel Ratio until warm. However, in my case, the O2s DID have some kind of affect on start up. I think it's has to do with After Start Enrichment ASE, (thanks Br3w City) which is what old school guys would call a choke.

From the limited info I found, ASE is a table that is used to get the engine started and up to temp then the ECU would take over Air Fuel Ratio. Again, not much info out there. So I think ASE uses the heater in the O2 to heat up the sensor so the ECU can run the ASE table. My stumble was only for first 45 to 90 seconds or so. But the O2 heater did not work on my sensor and caused a rich mixture on that side of the engine. Here is the test I used for the heater check.

https://www.motor.com/magazine-summa...cuit-failures/

Also, in my case the sensor that caused my stumble was a Denso sensor installed during engine swap. But I think the exhaust shop I used may have welded the O2 bungs in with the sensor in place, there by damaging the heater part. I replaced with ACDelco and immediately cleared up problem.