>>>>Believe this at your own risk..
Here is my thoughts.. The fuel of the '90's did not contain Ethanol .. Ethanol 'thins Out' Gasoline, lowering it's BTU content PER GALLON.. the fuel now has about 10% Ethanol in it.. The Fuel Injectors feed Fuel on a PER GALLON basis, so to get a 'REAL' gallon of fuel, you need to actually add MORE than a gallon of Ethanol and Fuel..
The Calculations of the amount of 'Liquid' that is Squirted into the engine is the K Factor of the ECU Values.. Normal NA 'K' Factor is 411 ( Just a number ).. in order to 'Fool' the ECU into feeding MORE LIQUID into the engine, the K Factor needs to be raised.. I've fooled with my 3 running NA Z's, and the Stable number that works on all three of them is K of 435. This causes the ECU to inherently put more fuel into the Calculations..
It all gets double checked and Fixed by the O2 Sensors and Calculations any way so what does it matter?.. Well I have found it matters at IDLE only.. and it matters how the ECU settles into a Stable Cycling Idle Mixture Closed Loop Idle..
Normally my NA's were running at about 110% Fuel Trim.. with the K of 411.. By Raising the ECU's K value to 435, my Fuel Trims run usually at 95 to 102 %.. and USUALLY i'm able to keep a Stable Closed Loop Cycle at idle..
I've found that really heat soaked engine on a hot day, Idle my not cycle till things cool down.. I have thought it's because the Air Intake does not have a Temp Sensor, so ALL of the air temp corrections have to be done by the O2 Sensors, and the 'Spread' of the Calculations seems not to be very wide..
Now, back to your car..
If you hook up the Conzult Cable to the ECU.. watch the O2 Sensor Voltage.. the O2's should cycle at fast idle.. this says the ECU is happy, and all is well.. as the engine settles into Idle Mode, the o2's will stop cycling and GENERALLY fall to a low Voltage ( Lean Condition ).. what Id like you to watch for, is does the 'Stumble' happen when the O2 Sensor Voltage starts falling below about .2 Volt.. that would indicate to me a Lean Stumble..
Also look to see if Both O2 Settle to about the same Voltage.. IF they do not, that says the Butterflies are not set right.
Remember, the LEFT T-Body feeds the Right O2 Sensor, and the Rich Side is the High Voltage Side..
I have a Moates Chip in my NA ECU's so I can change the K Value on the Fly.. I Set the T-Body's to give me the Same O2 Sensor Voltage at Idle ( Somewhat ) and I set the K Value in the ECU to keep the O2's Cycling..
Please post your Findings..
Cj
