doesn't want to stop...

I just bought an SEL 380 ('81) for $1000. It's in really good condition, but I am noticing a problem right away - it seems like the throttle is kind of sticking...like at a stand still, its revving at 1500, but sometimes at
a standstill it only revs at 500. When its revving like that, you go to put it into gear and the car literally jumps ahead or back after what seems to be about two seconds (especially in reverse). Now I'm not a big engine buff - especially with this engine - it kind of looks like a brain, but does anyone know what this would be...transmission, modulator valve, or something to do with the throttle itself? I would really appreciate any feedback. Thanks. I should mention that it drives/shifts gear perfect on the highway.
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The engine should idle at about 500 - 700 rpm. The "problem" is that it doesn't; there's nothing wrong with the transmission. Fix the idle and the problem will be fixed too.
Different models have different ways of controlling the idle speed. Some have an electronic module and their circuit boards dry out and the solder joints crack - so one day its fine and the next its not. There are some rebuilders of such idle speed controllers - if that's what's installed in your model.
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Hey. Thanks a lot for your feedback. Something to add to my first question though...when I'm driving in the city, going from a standstill, it seems that I have to give it quite a bit of gas to start moving, then it "jumps" (not so much slams) into the next gear. Then as you get going and take your foot off the accelerator, the engine doesnt seem to slow down - it will even pick up speed if I'm going under 40 k. Is this still associated with the idle control computer? Also in your opinion, what would be the best way to go as far as do it yourself repair manuals?...I tried to track down a Haynes manual, but was told that Mercedes stopped making them - which I found funny because I didn't think that the companies themselves had anything to do with the manuals.
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The best manuals for these cars are made by Benz (with bootlegs all over ebay, I think it's $150 from Benz and $40 off ebay). Benz publishes their own manuals, and the Haynes ones should be seperate, but I wouldn't waste my time with those. I'm going to say your shifting issue is because of the idle. Get that fixed, and so should everything...I would also be sticking it in neutral when I stop in the mean time. Oh, and those idle control computers can be gotten from benz junkyards for cheap.
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Fix one thing at a time, otherwise you'll never know what was broken.
Don't waste your $ on a Haynes, buy a used M-B manual if you really want the "right stuff".
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Right on... You can get MB manual on CD now... just like Marlinspike said.
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Fairly easy fix, but I forget how (I know how if yours was a 82 or later but the 79-81 are a little different).
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You need to replace your idle speed control computer... it is located at the middle in between your two firewall when you open up the hood. Very common problem.
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Bare with me on this one, gang - When's the last time your transmission fluid & filter were replaced, Derek? Has it been longer than 30K miles? If so, I'd have the transmission serviced first before I spent anymore money on anything.
I seem to recall having a problem with my tranny slipping in & out of gear at a stoplight (with similar differences in idle RPM depending upon whether the tranny was still in gear or not). Upon servicing the transmission I found some cork gasket material had broken off & lodged in the filter intake - resulting in substantially reduced fluid flow. Replacing the filter and fluid restored normal transmission operation with no more delayed shifts into gear from a standing start, and an idle speed consistent with being stopped while in gear. Reading through your posts, I'm wondering if perhaps your problem is the same as the one I just described? Problem may be neither the transmission nor the idle speed controller, but just a clogged tranny filter. Same symptoms.
Jerry Wolfram '78 450 SL - 214K miles
Derek Pigeon via CarKB.com wrote:

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