Throttle Return to Idle

[ramcdonald]

My 71 280sl, manual, has recently "decided" to idle at high and variable RPMs.  After searching for "idle" and "throttle linkage" I've cleaned and lubricated all the linkage ball joints except those under the exhaust manifold which connect the vertical linkage to the throttle linkage and the linkage just above the starter motor (can't reach these).

I am suspecting that I've lost (knocked off?) some throttle return spring.  If I depress the gas pedal to the floor, then release it, (engine off), the throttle will only return to approx. 1/2 open.  I've found two springs - one at the venturi valve and one at the driver's side firewall.  Are there other springs that would more forcefully return the throttle to proper idle position?

Full disclosure:  I've replaced the starter about a month ago.  Don't think I broke anything in the process!
Richard

[A Dalton]

http://www.sls-hh-catalogue.de/bin/dbframes.phtml?mid=IN02

[Cees Klumper]

There is another return spring on the fuel injection pump itself, next to the two that you have noted. I don't think there are more than that, but without my car at hand I could be wrong. My linkage always returns nicely and is quite light to operate after all the cleaning and lubricating I've done to it. Perhaps the throttle linkage rod that runs against the firewall on your car needs to be lubricated? Maybe you can pinpoint the problem by disconnecting the various sections and trying them for ease of operation.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[ja17]

Hello Richard,
The pivot under the exhaust manifold is notorious for becoming dry and binding. Try checking it.

Joe Alexander
Blacklick, Ohio

[J. Huber]

Can anyone elaborate on what "lubricating" the pivots means? WHat to use, etc.

James
63 230SL

[rwmastel]

I think there is a preferred type of grease, but I can't recall what it is.  I've been told that simple ATF fluid is a good start if you don't have the recommend grease.  Of course, use your favorite cleaning agent to clean the ball & socket joint of any old grease, grit, or grime.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[ramcdonald]

All:

Thanks for your suggestions.  I was able to isolate the problem to the hinge (if that is the right term) on the passenger side firewall.  I think the technical description is "crudded up".  Anyway, after removing it, cleaning, doing a little polishing with steel wool, and lubricating it with some marine grade grease I had around, the whole system now works smoothly.

I was able to get at the lower linkage connections, under the exhause manifold.  They were indeed dry and dirty.  Cleaned and lubricated these as well.

thanks again!
Richard