AFR reading lean, AFR table showing rich..., guessing an exhaust leak? Other options? Options

[VaccaRabite]

As I get closer to Dyno Day for my 914 (July 22), I have a theory about some of my drivability issues.
This car has modern EFI, not carbs or Djet/Ljet. It’s running MS2 through a Microsquirt controller.

The car is clearly very rich. It bogs heavily coming off idle, to the point that it will sometime stall out if you don't dance the accelerator pedal just right at a stop sign or a traffic light. Last oil change I could also smell gas in the oil. And while Bob Hill ( @saigon71 )was driving my car the other night I occasionally saw puffs coming out of the muffler on overrun. Kinda cool, in a way, but not great.... lol.

I hooked up my trusty ancient tuning laptop and opened up the AFR table while looking at the AFR meter. Where the table is showing ~13, the gauge was swinging ~15.5, especially just off idle, when the car got hot.

So my theory is that the ECU is reacting to a false LEAN condition and dumping huge amount of gas into an already rich environment.

So, my possibilities are:

1. Exhaust leak at a joint
2. cracked SSI exchanger (UGH)
3. incorrect values for the AFR entered into the ECU (I doubt this one, given that the issue gets worse as the engine gets hot)
4. Some issue I have not thought of yet...

@mcmark
@Eric_Shea
@Mark_Henry
@chrisfoley

Thoughts?

Zach

[Mark Henry]

What WB do you have?
How old is the lambda? 4.2 or 4.9 LSU?
Have you been running the engine with no power to the lambda? (bad)
What are you using for a TB? dual TBs have similar sync issues as carbs.
How much advance on the timing?
Are you 100% sure of your wiring connections and grounding?
How far is the bung from the head?

The WB usually only has 4 wires but some have more, the WB signal is a just number between say 0.60 to 1.40 and the gauge does the math, I'd assume MS has a setting for type of fuel, 14.7 for gas and does the math as well.
BTW it's very simple math, a reading of 1.0 X 14.7 = 14.7 AFR that you see.

The two different readings are odd.
The fast swings of the meter Vs ecu may be normal, my SDS O2 ecu reading seems to dampen the swings compared to the meter, but they're the same reading.
I'd expect even if the meter had an error the same number would be showing on both the meter and ecu.

[Mark Henry]

dp-