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Discussion Starter · #1 ·
I'm having a problem of my revs dropping at idling and having to shoot back up again (irregular idle) when I switch on anything electric-hungry in my car.
Stuff like switching to a higher air-con fan speed, wipers, high beam, stereo etc will all cause my idle revs to drop and the engine will automatically compensate by revving up. Never happened before...
What could be wrong? I've checked the battery voltage when the car is running and not, and its more than adequate(14.5V, 13.5V)
The irregular idle is driving me crazy!
 
G

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Sticking idle speed control valve. When the car needs more power this valve opens to allow more air into the engine to overcome the increased load. If the valve is gummed up or dirty it will not respond as quickly and the revs will die back before the valve opens. Don't know how to clean it on an Alfa but the usual method is to remove it and spray with loads of carb cleaner.

Andy
 
G

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The butterfly valve is in the main airflow pipe from filter to engine and controls the amount of air entering the engine. It is controlled by a throttle cable connected to the accelerator, or an electronic stepper motor controlled by the ECU via the accelerator pedal(on fly by wire cars)

The idle speed control valve keeps the engine running when the throttle butterfly is fully closed. It usually bridges this butterfly valve and contains either a secondary butterfly valve or a solenoid controlled plunger. It can often be identified by the noise it makes on start up. They tend to twitter a little opening and closing rapidly in many installations (e.g. Ford) Again this is generic info, not Alfa specific.

Andy
 
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