Looking for idea on 75 450SL high idle

[John Gregg]

am a long time Mercedes enthusiast. I have mostly worked with diesels, and M130's and M110's.
This is my first 107, a 75 450SL. I got deal on a clean car. One of the major reasons it came with a $3800 estimate for new under hood cats from Midas. I bought a of 78 manifolds from the local salvage yard, still need to put them on. Car is grandfathered in now for emmissions.

It has the distributor with the two vacuum inlets. The hose is missing from
that regulates the idle after warm up. It would be a look it up in the book, and/or look at another 450 of the same era.

But I live in an area with great Mercedes salavage support. Any ideas on just bypassing or replacing/altering the two inlet vacuum control on the 75 450SL distributer? On our 72 250C we took the advance from an older M130 with the single inlet and are quite happy not to deal with a maze of vacuum hoses, sensors and switches. It rarely gets very cold in Texas and the SL is going to be a daily driver on nice days only.
John Gregg

[cth350]

one's advance and the other's retard. Get an older distributor or a newer one (with HEI). The newer kind will need new ignition compontents to go with it salvage them from the same car.

As for high idle, that's controlled by the amount of air getting in. The air is supposed to be controlled by the big screw at the front of the motor (follow the ducting). Leaks will of course, mess that up entirely.

If you've not done so, replace the rubber tips the injectors sit in along with the larger rings.

-CTH

[John Gregg]

Thanks for the advice. Hopefully the 75 450SL will be on the road in time for warm clear days. I plan to get the factory CD.
John G

[psfred]

Make sure the throttle position switch is working corretly (must be closed at idle) and that someone has not jiggered the linkage to hold the throttle valve open at idle. Throttle valve must be completely closed, and you MUST eliminate all idle vaccum leaks (including missing hoses, door lock vacuum line, etc) to set the idle speed and mixture correctly.

The fuel should shut off above 1500 rpm -- when coasting down from say 35 mph or so, you should feel or hear the engine "start up" when the fuel turns back on.

Peter

[John Gregg]

Originally Posted by psfred

Make sure the throttle position switch is working corretly (must be closed at idle) and that someone has not jiggered the linkage to hold the throttle valve open at idle. Throttle valve must be completely closed, and you MUST eliminate all idle vaccum leaks (including missing hoses, door lock vacuum line, etc) to set the idle speed and mixture correctly.

The fuel should shut off above 1500 rpm -- when coasting down from say 35 mph or so, you should feel or hear the engine "start up" when the fuel turns back on.

Peter

Quite a few of the lines have been toasted by the underhood cats, soom to be gone.
thanks,
John