Tuning With An Air/Fuel Gauge

[chaseincats]

Here's an interesting observation.  Every so often (a handful of times since finishing this project) I've noticed the car running more lean than usual (in the 16s instead of 14s).  Any idea why that would be?  All the contacts are clean and literally the only thing I do to fix this is shut the car off and just restart it - then the computer behaves properly.

This has literally happened maybe 2-3 times since I was able to read the engine's a/f ratio with the gauge and is a non-issue since a restart fixes it but I am curious.

Reminds me of "The IT Crowd"'s famous line, "have you tried turning it off and on again?"

Edited June 27, 2021 by chaseincats

[Patcon]

What are the outside temperatures when this happens?

[chaseincats]

1 minute ago, Patcon said:

What are the outside temperatures when this happens?

Yesterday was pretty hot actually - mid 90s.

[Patcon]

Get some compressed air and cool the ECU when it does it and see what happens

[chaseincats]

1 minute ago, Patcon said:

Get some compressed air and cool the ECU when it does it and see what happens

Will do.  Why do you think a restart solves it though?

[Patcon]

Wild guess is that it cools off some

[Captain Obvious]

Hmmm. Interesting. And no idea why that would happen.

So have you driven the car with this "lean boot" condition? Does it stay lean the entire time? Or did you shut it off and restart as soon as you saw the issue?

[chaseincats]

3 minutes ago, Captain Obvious said:

Hmmm. Interesting. And no idea why that would happen.

So have you driven the car with this "lean boot" condition? Does it stay lean the entire time? Or did you shut it off and restart as soon as you saw the issue?

Lean boot is a fantastic way of describing this.  Yeah it literally will run lean for the duration of that boot.  I ran it like that for my entire trip then when I got in the garage I shut it off and immediately turned it back on and it dropped back down into the 14s.

[Captain Obvious]

Crap. That's the wrong answer.  Haha!!

I was kinda hoping you re-booted it right away and it went back to normal. I think that would be easier to figure out. (Not easy, but easier? Maybe?)

So I got nothing right now... I'll think about it and see what I can come up with? Or maybe someone will chime in with some uber-smart theories? 

Not temp related... Not vibration related... Not system voltage related......... I wonder if my thinking cap will fit under my aluminum foil deflector beanie.

[Captain Obvious]

This is a 78, right? With mostly stock EFI system?

[chaseincats]

9 minutes ago, Captain Obvious said:

This is a 78, right? With mostly stock EFI system?

Yep.  The only thing not stock about it is the tuning we all worked through on this thread.

[Captain Obvious]

Gotcha.

I'll think about it, and the meantime, let's hope someone else knows exactly what's going on!