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  #1  
Old 02-22-2001, 10:47 AM
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Location: AL
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Hi All,

I have a 1991 300E. It's been a great car. It has developed a problem, though.

The idle cutoff will not work. Until...you press the accelerator to the floor one time. No need to hold the accelerator down for any length of time; just a split second will do.

After you conduct the "Accelerator Maneuver", Idle Cutoff works perfectly.

The throttle position sensor and decel switch are functioning properly.

Pretty weird, huh?
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  #2  
Old 02-22-2001, 09:01 PM
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Location: Suwanee, GA, USA
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You have a problem with the linkage, spring or switch. I have seen all of them fail from time to time.

You should lube the linkage by taking all of the balls off and adding grease.
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  #3  
Old 02-24-2001, 05:50 PM
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The linkage is free and clear. The throttle completely closes each time. The decel switch is new because it was working intermittently and it is working perfectly. Throttle Position Sensor is working properly; always 0 ohms between pin 1-2 when throttle is closed.

Even though all these items are working properly, the car still fails the test (short pins 1-2 on TPS, 2500 RPM, press decel switch & engine should "hunt"). After flooring the accelerator briefly, the car then passes this test.

Flooring the accelerator for an instant ALWAYS "fixes" it. Idle cutoff works perfectly after that. At least until next time you drive the car.
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  #4  
Old 02-24-2001, 09:18 PM
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Your terminology is screwing with me. First I presume you are talking about decel cut-off and second I presume you are ohming the throttle switch (off-on switch) not the airflow potentiometer. The airflow potentiometer plays a part in decel cut-off and could very easily be affected by your full throttle maneuver. I watch the decel cut-off function with a ampmeter on the EHA. I do this while driving with a ten foot leads on my meter. I say this because some models also integrate the speed sensor on the back of the speedo into the calculation and will not decel cut-off below a certain speed.
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  #5  
Old 02-25-2001, 01:20 AM
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Pardon me. Yes, you are correct. It is the DECEL shutoff.
I am ohming the throttle valve switch (pin 1-2).
The test I decribed is straight from the MB Service Manual, Engine 103.
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  #6  
Old 02-25-2001, 02:01 AM
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I would caution that the engine manual will not reflect all the various changes in the KE system. Those specifics would be located in the diagnostic manual and/or ETM.
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