DFCO is an acronym for "deceleration fuel cut off"
It's programming in the engine computer that allows the fuel injectors to turn off anytime the car has enough momentum to turn the engine at a runable speed.
How does the car drive the engine?
The engine and tires are physically linked in a manual transmission car anytime the transmission is in gear and the clutch pedal is not pushed in. If the car is moving forward and you take your foot off the gas, the car is now driving the engine with its momentum.
So what's it mean?
Your not injecting fuel and saving money
Why bother measuring it?
Because another member (eggman) and I both noticed the same thing. Odd readings from scan gauges when coasting vs dfco. - Not every car is equipt with dfco. I do not believe it would show up on EPA testing, so the car manufacture has little to no reason to add it. - i have read some cars have DFE (deceleration fuel enleanment)
How to measure it?
A multimeter set to dc hz measurement, with the test leads PARALLEL to across the load. This measurement gives you the amount of injection cycles over a period of 1 second
i stuffed wires into my injector connector. Done, easy. Just be careful because if you short the wires your car will suffer some sort of damage.
This thing DFCO's like a mother.... From any RPM down to approximately 1200 rpm. I did not notice any "not until warm" or any other charactoristics.
What did i learn?
The ultragauge is simply incorrect in its readout when DFCO is happening.
I've been driving wrong this whole time coasting with the clutch in up to stoplights
Im a nerd
1- warm idle
2- 2nd gear full throttle full rpm ( was a bit higher bad photo time i think it hit 58)
3- wired into injector
4- DFCO happening