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, Mon, 18 Nov 2002 02:45:13
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AF too lean is one of the adaption faults that the ECU can post when it is not able to get the O2 sensor signal to the target levels by changing the injector dwell. In some cases the O2 senor target levels might be achieved but the injector dwell to to it might be out of acceptable limits, depends on how they set up such features.
So what can cause this? A vacuum leak would provide more air, and perhaps a fast idle, but the ECU would see manifold pressure and the mixture should be perfect. If the vac line for the MAP sensor has a leak, then the MAP sees maybe a higher pressure than actual when off boost, and lower than actual when on boost. So there will be an adaption failure and perhaps a limp home mode. If the fuel pressure is too low, things can get lean. A bad fuel pump, fouled fuel filter or a bad fuel pressure reguator. Whoever decided that a too lean fuel adaption fault means that both O2 sensors need to be replaced is not very experienced. One cause is a resistive contacts from the sensor to the threaded fitting is screws into. But installing new ones will take care of that. But there could be resistance in the exhaust system at the downpipe to turbo, or turbo to manifold etc. Someone needs to check the resistance from the sensor hex bodies to ground, and chase down the resistance if fould and fix that.
There are things that will cause adaption faults in perfectly good O2 $sen$or$.
Injectors clean?
posted by 207.43.195...
, Mon, 18 Nov 2002 02:45:13
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