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Registered User
Join Date: Jul 2011
Posts: 5
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Idle speed higher and smoother with AC on?
I have a 1999 996/3.4. When I have the AC on, it idles about 100 RPM higher and considerably smoother than with it off. When the AC is off, the idle gets low enough that the car tends to tremble a bit at stop lights.
I can turn the AC on and off and clearly see the idle speed change and get smoother and rougher. Why is this? Is it normal? |
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07-29-2011, 07:38 AM
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Registered
Join Date: Aug 2010
Location: Earth.............
Posts: 2,908
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The DME raises the idle speed with the A/C on to compensate for the drag the compressor places on the engine. This is completely normal.
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Accrochez-vous bien de vos rêves..........." |
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07-29-2011, 08:03 AM
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Registered User
Join Date: Jul 2011
Posts: 5
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Should it idle rough normally? The car tends to shake a bit, and that seems odd to me.
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07-29-2011, 08:18 AM
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Registered
Join Date: Aug 2010
Location: Earth.............
Posts: 2,908
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No, it should idle smoothly. Without seeing a scan of the car's DME, it is difficult to know what is wrong, but the possible list is just about endless..............
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Accrochez-vous bien de vos rêves..........." |
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07-29-2011, 08:45 AM
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