Almost met Jesus this AM due to a faulty thermostat!

[BlazerBill]

If I’m understanding the discussion correctly, the EFI system shut the engine down because of an AFR condition in cold weather due to a T-stat that had the very small thread in it preventing it from closing. This doesn’t make sense. I don’t run EFI on my squarebody’s and am not very technically savvy on EFI although the downsides that I am aware of prevents me from incorporating it. Assuming this is what happened, then the EFI saved the engine by shutting it down but at the sacrifice of human life???!!! If that is the case, it makes me concerned that modern aftermarket EFI systems aren’t (fully) compatible with legacy mechanical braking and steering systems whereas, new vehicles have electrical safety features built into these systems to prevent or reduce the risk of injury or death in the event of an accident due to engine shutdown while driving. Could this potentially be the case with aftermarket EFI systems for older/antique vehicles?!!!

 

[SquareRoot]

No. It was no different than not having your idle screw set high enough and stalling the engine while its still cold. Difference is with a carb, you get one setting for the idle when the engine is up to temp. The choke is what makes it run during the transition. EFI allows you to set the Air Fuel Ratio at several (6+) engine temps or infinite if its on a curve. It's just that I had never had the opportunity to adjust it at temps (ambient air) below 38 degrees because it rarely gets that cold here. As with all efi tuning, you guess to get close but you have to drive it under actual conditions to get it right on. When any vehicle with power accessories dies it is much harder to operate. When you have larger tires and the brakes and steering are driven off the power steering pump, it becomes a LOT harder.
One thing about aftermarket EFI is that despite it being marketed as "self learn" it is NOT. There are thousands of parameters that need precise tuning. GM spends millions with the engineering department to make modern cars run seamlessly. Aftermarket is usually some knucklehead like me following some knucklehead on YouTube.

 

[BlazerBill]

I agree which is why I don’t install aftermarket EFI systems, among other reasons. There is not as much R&D spent on aftermarket systems as OEM and aftermarket systems aren’t user friendly to tune the “thousands of parameters”, as you say.