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  #1  
Old 10-15-2001, 05:58 PM
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RPM Surge while coasting

When my 560SEL is coasting, especially downhill, there is a very noticeable surging happening. The tachometer shows 200-300 rpm changes but you can feel it as well. Since it happens while coasting, it seems to be related to a sensor reading the high vacuum incorrectly. Could this be a problem with the oxygen sensor or some other sensor?

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  #2  
Old 10-15-2001, 07:02 PM
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For emission control there is a ""fuel shut-off"" durning decel, sounds like your car is turning this on & off too quickly.
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  #3  
Old 10-15-2001, 09:43 PM
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How would I adjust the fuel shut off?
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Old 10-16-2001, 11:57 AM
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You dont. The fuel cut off is controlled by the Lambda computer. Both of my 420's do the same thing. Its normal.
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Old 10-16-2001, 12:13 PM
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vrsmith,

Does the engine exhibit the same surging at a standstill idle?
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  #6  
Old 10-16-2001, 12:29 PM
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I won't say that the idle is perfectly smooth, but it doesn't seem too bad. It is only noticeable on the highway.
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Old 10-16-2001, 11:24 PM
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My friends 1995 S320 has the same problem.He asks me to fix it every time i drive in the car with him.is it normal
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Old 10-17-2001, 10:13 AM
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Its normal.
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78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k
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  #9  
Old 12-01-2001, 09:41 AM
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This behavior can't be normal; at least not to the extent that it happens with my car. When I first got it, it didn't do it at all. Now I feel it is quite prominent. I'm thinking of changing the oxygen sensor first since it is easy to do and likely due since they are rated for 60K or so.
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Old 12-01-2001, 11:27 PM
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My suggestion is to make sure that the throttle "closed switch is working when hot. I have seen them fail in this manner.
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