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  #1  
Old 12-14-2009, 11:27 AM
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'72 280SE 4.5 > Throttle Control Linkage

This is my first post to the forum. However, since acquiring our 108 "project" I have spent many hours researching this site and it has proven to be invaluable in understanding the cars design and troubleshooting our numereous problems. Thanks to all that contribute their time and knowledge to the forum.

I am working on the throttle linkage. The symptoms are:
1. The throttle regulating rod does not start to move until the pedal has traveled ~2".
2. With the accelerator pedal all the way to the floor the throttle is only open ~75%.

After studying the parts diagrams and researching this site I have figured out that I may be missing a rod seat or something where the regulating rod pushes against the firewall. (see pictures below)

'72 280SE 4.5 > Throttle Control Linkage-img_0948sm.jpg '72 280SE 4.5 > Throttle Control Linkage-img_0952sm.jpg

With what I have left I am not sure how this was supposed to be originally.

Thanks in advance for the help.
_____________
Porter Fell
1972 MB 280SE 4.5
1972 BMW 2002tii
1987 Porsche 911 Carrera
1956 Willys Jeep
1967 Travco Motorhome


Last edited by pfell; 12-14-2009 at 11:40 AM.
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  #2  
Old 12-14-2009, 12:02 PM
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Location: Dallas, TX
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You're missing the bushing that goes on the end of the rod. It's a plastic ball with a hole cut in it in which the rod slides. You can probably get both of these parts for under $3 or $4. Call Phil at Fastlane, he'll be able to hook you up.

Also, please post a picture of the rest of the throttle linkage, in particular the other end of the shaft you have pictured, where it goes on the engine. I think I may be messing something there and want to compare.

Thanks,
David
Attached Thumbnails
'72 280SE 4.5 > Throttle Control Linkage-1233010022.jpg   '72 280SE 4.5 > Throttle Control Linkage-1263000085.jpg  
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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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Old 12-14-2009, 12:03 PM
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I'm not sure exactly where that first bushing goes, but I think it goes under the pedal. It sounds like you're best off replacing all those bushings since they're so cheap.

Best Regards,

David Peden
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2000 Honda Accord V6 137k miles

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  #4  
Old 12-14-2009, 12:49 PM
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See if these help:
http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/18505d1085103225-picture-request-dscf0123-.jpg
http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/18504d1085103164-picture-request-dscf0122-.jpg
http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/18503d1085103143-picture-request-dscf0121-.jpg

And here's the directions for the linkage lengths - all mine are within 1mm of values suggested.


1) Disconnect all the linkage rods
2) Check to see if the throttle closes completely without biting. If it's open or if it sticks, adjust it with the idling speed stop screw (SS)
3) If you adjusted the throttle, re-calibrate the throttle position sensor
4) Adjust the control rods to these lengths:
1: Regulating rod = 78mm
2: Regulating rod = 114mm (auto tranny; 90mm manual)
(Then reconnect)
5) Adjust the regulating rod (#3) so that the throttle valve lever rests on the idle speed stop screw, and there is full clearance at the stop (if you push lightly on the pedal, no throttle opening occurs until the clearance in here is gone).
I think that's a clearer explanation than the book gives!

To adjust the kickdown lever, disconnect it and push it as far back (towards firewall) as it can go, and adjust the ball head so that it rests perfectly over the stud at this point. I backed mine off 3 revolutions from this to shorten the rod for a little higher shifts, clearing out low-RPM shift-jerking.

Picture with labels for these:
http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/18507d1085104722-picture-request-labeled.jpg
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Old 12-14-2009, 04:05 PM
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Tomguy, is there anything that goes on the throttle rod where it enters the intake piece? I'm talking about the same part that pfell is, just the other side of it, where it connects to the manifold. Mine has no bushing there, just that copper colored piece that unbolts allowing it to slide back from the manifold.
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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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  #6  
Old 12-14-2009, 04:07 PM
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I removed the regulating rod to check the end nearest the throttle body. Here is what you have:

'72 280SE 4.5 > Throttle Control Linkage-280se-016sm.jpg '72 280SE 4.5 > Throttle Control Linkage-280se-018sm.jpg

I also located a more accurate diagram in the Haynes manual. I am going to order the ball sockets and bushings for both ends.


Thanks,
Attached Files
File Type: pdf Throttle Control Linkage-efi.pdf (371.7 KB, 330 views)
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Porter Fell
1972 MB 280SE 4.5
1972 BMW 2002tii
1987 Porsche 911 Carrera
1956 Willys Jeep
1967 Travco Motorhome
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  #7  
Old 12-14-2009, 04:45 PM
Brian Ostosh
 
Join Date: Mar 2007
Location: San Diego
Posts: 504
Balls on each end
AND most important for throttle....is
Replace motor mounts and trans mount
The motor MUST align with chassis for the throttle to be proper
Check the fan to shroud position top bottom side side
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  #8  
Old 12-14-2009, 05:29 PM
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Oh wow. Thanks pfell. I've bookmarked this page and can't wait to check out my car tomorrow afternoon!

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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