ECU Recalibration

[ToothbrushMan]

Does an ecu need some miles under its belt to recalibrate itself to a brand new OE lambda sensor or should it be spot on from the get go?

i was running rich (plugs were dry black and very sooty) and got a lambda fault code but CEL light.

[GreenV8S]

It might need some time to 'un-learn' a bad long term adaptive trim, unless it was reset. However the short term trim should compensate for that fairly well if the system is working correctly. If you're still seeing plugs getting fouled after replacing the lambda sensor, maybe that wasn't the only problem or maybe the problem was not in the sensor itself. The ECU will probably be showing active fault codes if it is over-fueling that badly.

[Sardonicus]

No it should sort itself once it goes into close loop not long after start up and trimming, however remember if you have a misfire for example the 02 sensor will send the ECU rich due to excess oxygen (thinks engine is weak/lean) in the exhaust and hence black spark plugs causing further misfiring , its a dreaded loop IYSWIM , correct info can be caught in live data

[stevieturbo]

Not as such...but it depends on actual fault and the car/ecu itself.

It may heave learnt and been using very bad long term fuel trims trying to correct a problem...which now have to be unlearnt, unless the ecu has been reset.

It shouldnt take a very lonng time though

[Sardonicus]

stevieturbo said:

Not as such...but it depends on actual fault and the car/ecu itself.

It may heave learnt and been using very bad long term fuel trims trying to correct a problem...which now have to be unlearnt, unless the ecu has been reset.

It shouldnt take a very lonng time though

Should start making those corrections not long into a drive however

[stevieturbo]

Sardonicus said:

Should start making those corrections not long into a drive however

It "should"....but not definitely it will.

And depends if all faults have been corrected, which isnt always easy to ensure, and there could have been more than one fault causing incorrect fueling to start with.

[Sardonicus]

Agreed