I know there is a Lambda (O2) sensor in the exhaust head pipe. Is this just to confirm that SOME O2 carries through (ie; all the fuel was burned) for emissions control purposes? Or does it also tell the ECU to increase the fuel pump delivery to richen the mixture? I have my doubts about the latter. Is the ECU algorithm sophisticated enough to respond to fuel mixture variations? I can't see how it knows what is in the tank, other than via the Lambda sensor. Your thoughts?
For what it's worth, the ECU doesn't vary the fuel pump pressure to control the fuel flow. The pump runs at a constant 294 kPa (42.6 psi) pressure.The ECU controls the electrical pulse to the fuel injector adjusting how often/long it remains open.As for the 10 percent alcohol fuel, that's all we've had for several years here in Phoenix, Az and it hasn't caused a problem yet.I'm just guessing but I know the Fuel Injection system and ECU were designed (and built?) in Japan. They've been dealing with this gasoline/alcohol fuel mix for many years now so I'm betting they set up the maps to cope with this issue, at least for the 10 percent mix.
..........ethanol...... It's a fine hydrocarbon, and I'm quite fond of it.
wash, rinse, repeat ..... thousands of times per minute. Love that.....
Thanks to all for your helpful input, especially GHG and Gremlin. I now have 5 areas for experimentation, not necessarily in sequence, after laying down a repeatable baseline test run for comparison:1. Try a dose of Techron in a tank of E-10,2. Try a tank of straight gas (located a source nearby),3. Advance the TPS idle output voltage,4. Tweak with the idle air bypass screw, and5. Try temporarily disabling the lambda sensor.Are there potentially harmful downsides to #5? If, as Ekatus thinks, the ECU control strategy on lambda is simply to control emissions, I would think I could test this case for impact on my problem (engine stumble upon throttling up from idle) without harm. If, as Gremlin says, the ECU is using lambda feedback to keep nudging the AFR just barely lean of stoiciometric, then disabling the sensor might cause the ECU to drive the fuel pump output to the limit of the map range, one way or the other (max or min) - much smoke or knocka-knock?I appreciate your further input on this, and I will post my experimental findings as I make them - now that last night's snow is gone!