Originally Posted by twolostminds
I'd like to know if I understand the FEH's warmup stratagy correctly...
After starting a cold soak engine the PCM will run the motor extremely rich until the coolant temp and catalytic converter rise to operating temperature.
If the above is correct, at what temp does the cat need to be for the engine to end the rich burn warm up stratagy?
On my 05 it runs rich biased with a retarded spark, but actual open loop operation is fairly brief. Then again, I have never been in particularly cold weather. The end of the warm-up mode, where propulsion is provided solely by the traction motor while the engine idles, appears to occur at a catalyst temp of around 680C. If you shut the vehicle off for more than 5 minutes or so, it will start out in warm-up mode again, even in warm weather. I have also noted the "drive-through" triggering of warm-up mode. This summer, while waiting in a drive-through I shifted into N when the SoC was nearing 40% to keep the ICE off. While waiting with the radio and blower going, the SoC dropped to 38%. When I drove away, I wasn't paying attention to the SG and got up to 40MPH pretty quickly due to traffic. I hit CC and then glanced at the SG to see 31.3% SoC! So it had entered warm-up mode despite it being 105F outside at the time. This scenario was repeated several times so it was definitely not a fluke occurence.