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From a factory sevice manual Posted by Doug [Email]  (#3538) [Profile/Gallery]
(more from Doug) on Wed, 29 Aug 2001 18:21:28
In Reply to: Rough start, idle, then fine, Orion, Wed, 29 Aug 2001 13:58:26 Members do not see ads below this line. - Help Keep This Site Online - Signup |
This is long and technical. I quote from the Saab Factory Service Manual "The air mass meter is fitted between the air cleaner and the inlet manifold. It consists of an aluminum housing enclosing an air duct. Located in the centre of the duct is a tube which houses the platinum filament. Two fine-mesh filters are fitted in the duct, one upstream and one downstream of the filament.
The temperature of the filament is maintained at a constant 100C(approx)above that of the inlet air, regardless of the composition of the air or the flow.
Since the filament is sited inside the inlet duct, it can become coated with dirt, resulting in a deterioration in its sensitivity. To keep the filament free from dirt, it is heated to a temperature of approx. 1830F for a duration of one second. This takes place automatically, four seconds after the engine has been switched off. After completion of the burn-off function, the system relay opens.
The device for controlling the current required to keep the filament at a constant temperature consists of a bridge circuit and a detector resistor, the voltage variation across which is directly proportional to the magnitude of the inlet air mass.
The electrical components are integrated in the air mass meter housing, which also incorporates a potentiometer (accessible from the outside) for adjustment of the CO content at idling speed.
In the event of the ECU failing to receive a signal from the air mass meter (e.g. because of a broken filament), thhe limp-home function will take over to enable the car to continue its journey, although with somewhat impaired performance."
What does that all mean? If that's the problem source Ive been dealing with it for a couple of months. It doesn't seem to happen once the engine is warmed up, so its manageable.
posted by 24.51.7...
, Wed, 29 Aug 2001 18:21:28 <-- Viewing This Message
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