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Old 07-08-2005, 01:28 PM
Join Date: Jun 2005
Location: Buffalo, NY
Posts: 68
Purpose of the throttle...

Being that my '77 300D is the first diesel I've ever owned (for the past four months) I'm still trying to gain a little more knowledge on these cars. My question today is the purpose of the throttle knob on the dash. Whenever I start the car I keep the throttle as low as it goes then turn it up until the car starts. Do I have to do this - it seems that the car doesn't start as easy when the throttle is full bore upon start-up.

Once I'm driving I keep the throttle up all the way. I guess my question is - "Is there a optimum position to keep the throttle, and what effect does different positions have on the car (ie. oil consumption, gas mileage, etc)"

Thanks in advance everybody

'77 300D (259K)

'99 ML430

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Old 07-08-2005, 01:30 PM
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THats not a regulates idle speed....its more important in the winter than the summer....bout it should be set to the minimum unless you need it more to warm the car up when cold.
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Old 07-08-2005, 03:44 PM
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Haven't used mine in fifteen years I bet.

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Old 07-08-2005, 10:44 PM
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think of that knob has a manual choke. As mentioned, it really is needed in the colder temps. Set it as low as she can with out the car stalling when you first get her started.
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Old 07-08-2005, 11:04 PM
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Join Date: Dec 2004
Location: Columbia City Indiana
Posts: 345
Yes that knob adjust the idle. Turn it all the way CCW for high idle which is nice in the winter because you don't have to worry about keeping the engine speed up to keep it from dying. There is no other fuction associated with this knob other than adjusting the idle speed.

If you are having trouble starting then wait for a slow count to ten after the GP light goes out before you try starting. The relay keeps juice to the GPs for a while after the light goes out and after all of these years it isn't turning the light off at the right time.

1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C
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