I have a knob, looks like a plastic key, on the left side of the dash under the speedo. It does not move, it maybe frozen from lack of use. I am wondering what is it and what should it do?

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2000 VW Jetta TDI with 213,000 miles and climbing
84 300D non turbo getting ready for wvo conversion

Hmmmmm. on the 123 it might be different but what it sounds like to me is the idle adjustment knob. But it should move and be on the right under the speedo. At least on my 115. Hmmmmmmm.

Someone will know

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76 300D 130K "Stella" (Sold )
74 240D 299K (Donated to Highschool For Senior Project WVO)
83 300TDT 290K (My one and only)
Sanford, NC

idle adjust or hand grenade pin

idle

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

"idle adjust or hand grenade pin"

Well since it did not come out it must be an idle adjust That would explain why the idle is rough when it is cold outside.

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2000 VW Jetta TDI with 213,000 miles and climbing
84 300D non turbo getting ready for wvo conversion

Definitely the idle adjust knob. They are relatively inexpensive to replace since they do siexe up. It does help cold starts if you're not inclined to push down on the loud pedal to help start on cold mornings.

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

Yes its the idle speed adjustment and its a very handy thing to have. Wish the turbo models had them.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

idle speed adjustment... its on the left in mine too

The idle speed control may need to be adjusted and/or lubricated, and there is another trick: Hold the accelerator down halfway while turning the idle knob counterclockwise. It should move easier this way as it takes the tension off the knob itself. When turning it clockwise, simply turn the knob and it should move easily (you can actually watch the accelerator pedal release slightly).

I always wondered, too, why the turbo models don't have the knob...perhaps there is a cold start module/solenoid that automatically speeds up the idle when cold? The Peugeot diesel I used to drive had this...I remember when it stopped working

-AC
'76 240D

ohhh thats what that is. My dad thought it was a choke on his 78 300D. But we didnt pull it thinking thats what would shut off the engine.

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Current:
05 E320 CDI
07 GL320 CDI
08 Sprinter
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Previous
2004 E55 AMG
2002 C32 AMG (#2)
1995 E300
1978 300D
1987 300D
2002 C32 AMG(blown motor :[
1981 300SD
1983 300SD
1987 300SDL
2002 Jetta TDI
1996 S420
1995 S500
1993 190E 2.6
1992 190E 2.3
1985 190E 2.3 5-Speed

Thanks for the info. I was wondering if it was a turner or a push\pull. I sprayed the engine side with WD40, I figured that duct tape would not work in this application. I will try the go pedal and turning method in the morning.

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2000 VW Jetta TDI with 213,000 miles and climbing
84 300D non turbo getting ready for wvo conversion