do drive to long with it like that. If you unplug it your car computer will notice quickly. It'll the throw a CEL
and your car will go into "limp home mode'. Basically Your computer will know it's missing and it will actually try to guess mass airflow based on the other sensors that register. for more info see: http://www.fordfuelinjection.com/?p=64
, I have cut and pasted a couple excerpts:
Failure mode is a stand in strategy in the EEC
designed to maintain vehicle operation should one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the EEC
, memorized data from the computers KAM
memory will be initiated. EEC
continually checks the sensors against its records of normal readings during operating conditions similar to its current state. Hold on that sounds hard! Not really, randomly EEC
looks at the past to see if the engine is somewhat where it usually is. If for some unknown reason a sensor is off the charts, it canâ€™t be trusted. So instead of tuning the engine to a possible faulty sensor reading and harming the engine and drive-ability; EEC
replaces the sensor reading with a best guess from a past memory. This is why unplugging the battery to fix something works against you. Unplug the battery causes EEC
to memorize all the sensor data as base line and normal. If it memorizes a bad sensor it will take it longer to call it a liar. Ford did however give EEC
a very broad idea of what the sensor should be reading in its permanent ROM memory, so it will catch on to failed equipment sooner.
I am going to divide up the sensors into two groups. Ones that will cause failure mode but allow drive-ability and the sensors that will cause a no-start or barely drive. Actuators can cause failure mode to take over, but only if the failed actuator is giving a sensor reading way off the chart.
Now this one is a little complex. EEC
likes to toy with the fuel ratio at random. It does this to run complex math equations. She is calculating how much fuel is required to reach certain lean or rich states. Why you ask? Because playing this cat and mouse game with the fuel ratio allows us to fine tune the engine parameters in other strategies. Confused yet? EEC
cuts back on the injectors for a spit second and counts how long it takes for the HEGO
to report back a lean environment. EEC
leans and enriches at different amounts and get back different numbers. These numbers tell EEC
if the engine needs a tune up, or if youâ€™ve added a performance parts and allows us to actually alter the fuel amount delivered. What do we do with those numbers EEC
collected? Well there is a Table called â€śAdaptive Fuel Tableâ€ť (makes sense huh?) This table is used as a multiplier, it is held over the master load table. It then multiplies each number in the master table to get a better control of fuel delivery over time. In a computer that has been just connected to the battery it is full of â€ś1â€™sâ€ť, if you multiply the master table by â€ś1″ you get the same number. Iâ€™m not good at math
and I understand it, 14.7:1 X 1 = 14.7:1, simple!. After many days of driving on the highway it begins to fill with multipliers like â€ś1.2â€™sâ€ť and â€ś0.9â€™sâ€ť, which will alter the master table. Donâ€™t believe me? 14.7:1 X 1.2 = 17.6:1, and 14.7:1 X 0.9 = 13.3:1, and we just fine tuned our fuel curve without doing anything special. Isnâ€™t that cool? Well not always, this entire technology depends on the Oxygen Sensors being fresh, clean, new, and in good condition. And it canâ€™t be responsible for displacement changes, cam changes, or other big performance add-onâ€™s. This technology is only meant to keep EEC
on the same level as an ageing engine with diminished performance. It is not meant to be relied upon for performance engine tuning!