Got a GT35/40 and did some great runs and tuned to a good safe AFR. The idle runs around 12.0 but after driving and letting the car idle for a while, out of nowhere it will just die. I don't think it's in the tuning, but have no idea what it could be. The logs show nothing. Fuel related, ignition related, electrical (relay, fuel pump, ignitor, harness)???? Really lost on this one.

 

could be the ignition module/igniter is getting overheated and shutting down. If that's the case, it would need to be replaced.

 

Check your spark plugs too.

 

Idle AFR is too rich.

 

My T78 runs at 11.2 and won't die, what makes 12.0 too rich? Could you explain how that could be the issue?

Brand new plugs

 

I am not commenting on your engine dying problem which can not be determined over the forum. But I am commenting on your idle AFR.

11.8 to 12 AFR is what you run for boost in the 8-10 psi boost range.
Stoich is 14.7, which is most commonly used for cruise.

My idle is around 14 and 16 at cruise.
You want your idle at lean as possible to keep the plugs cleaner.
Actually you want as lean as posible AFR from idle through cruise to also get better mileage.

Only on boost do you need richer AFRs for power and safety.

 

yea, except for people like me who don't have control over idle afr with the PFC.... which really sucks! hey chuck, I've read some of your posts which say that the PFC doesn't allow small changes in the idle and cruise areas, but then I see that you have full control with yours, so how come you can do it?

here's my previoud posts: https://www.rx7club.com/power-fc-forum-47/problems-leaning-out-idle-497240/

 

You should have perfect control over idle AFR. It's idle timing that requires a special setup on the PFC with the ISC disabled or removed.

 

Idle AFR is one thing, but my main concern here is the fact that this car is completely shutting off. If anyone has any ideas that could actually help me troubleshoot this problem, I would certainly appreciate it.

 

So you datalog the car during this idle scenario and you don't see anything changing? I would expect your IATs to go thru the roof as it sits idling, the AFRs will vary somewhat during this IAT increase and perhaps something is not mapped right for this operating condition. Or perhaps some ignition component such as a coil is breaking down under that heat condition. Good luck with this one, it's hard for us at home to give you a definite solution unless we've had something near identical happen.

 

Check the volts on the battery, perhaps at idle with an UD pulley or weak alternator or batt you might be getting low volts.

 

the very crazy thing is that it doesn't sputter or anything. The car idles perfectly and it's almost as if the key was cut off. The turbo timer doesn't tick down and is never activated like if the ignition circuit was bad. It's the strangest thing I've ever seen.