High Idle, 1100 RPMs, How can I manually turn it down - PeachParts Mercedes-Benz Forum

zsmith29 · #1 09-06-2008, 12:25 PM

The little knob has broken off of my 84 300 D and I think my car is idling to high. How can I turn it down?

zsmith29 · #2 09-06-2008, 01:17 PM

I finally found a write up on this from back in '06
Now I need to go buy a 14 MM deep socket so I can adjust it down some

zsmith29 · #3 09-10-2008, 08:36 AM

I have gotten the RPM's at idle down. They are now at around 8500-9000 RPM's.
Is this optimal? Should I try to get it a little lower? My engine is still pretty loud.

Diesel911 · #4 09-10-2008, 10:37 AM

On my 84 300D the spec for idles speed is 750-800rpm.
I have no "little knob" that adjust the idle speed. Where is that knob located?
Terms:
Low Idle = the rpm the engine turns with your foot off of the accelerator (engine running normal of course).
High Idle (on other Diesel Engines) = The rpm that the Governor in the Fuel Injection Pump is set at and will start to cut off the fuel to your engine if you give it full throttle (to protect the engine against over revving). While there is and adjustment on the IP for this it is normally set when the IP is calibrated and often coated with tamper proof paint or has some sort of cap with a lead seal over the adjustment so they know if you messed with it.
I figured this comment must be a typo "They are now at around 8500-9000 RPM's."

zsmith29 · #5 09-10-2008, 10:54 AM

Yeah definitely a typo (850-950).
I think that the knob was on my car right under and to the right of the steering column. Near where you put the key in the ignition.

Biodiesel300TD · #6 09-10-2008, 11:36 AM

Quote:

Originally Posted by Diesel911

On my 84 300D the spec for idles speed is 750-800rpm.
I have no "little knob" that adjust the idle speed. Where is that knob located?

The early 123's had an idle adjust knob that would allow you to adjust the idle by 100rpm or so for those cold mornings. Not sure what year they stopped putting those in. Probably the early 80's. But 82 doesn't have one.

toomany MBZ · #7 09-10-2008, 04:17 PM

Quote:

Originally Posted by Biodiesel300TD

The early 123's had an idle adjust knob that would allow you to adjust the idle by 100rpm or so for those cold mornings. Not sure what year they stopped putting those in. Probably the early 80's. But 82 doesn't have one.

Yeah, I think the turbos don't have that.