280SL engine surge

[n/a]

I have a '69 280SL, automatic, mechanical fuel injection with 189,000 miles on it.  I haven't had it too long, so I don't know exactly how it is supposed to run.  At speed it runs great, though it seems to need another gear selection forward on the freeway.  I think that is just the way it is because the tach and speedometer line up in the top gear.

However, at low speeds, and particularly in slow deceleration to a stop, the engine surges at each down shift, to the point that you have to hold the car back with increased braking for a moment.  It's driveable, but uncomfortable.  The local MB dealer shop says that that is the way the car is and the degree to which the car pulls forward is the result of a old and nearly worn out transmission that needs replacement. I don't have a problem replacing the transmission, but I can't convince myself that the trans has anything to do with the engine surge.  I gotta think it has something to do with the interaction of linkage that controls the throttle body, the injection pump, the transmission shifts and the throttle pedal.

Can anyone shed any light on this problem?

Niles

[rwmastel]

Niles,

If your local MB dealer knows these old cars, that would be very unusual.  Most MB dealers don't want to work on (or train their techs on) cars older than 10 or 15 years.  There are exceptions.  I suggest you contact other members from Oregon.  Use the Members link in the top right and find - George Davis, Optimizr, & Dweezilb.  Click on their user name and send them e-mails.  Find out where they have their cars serviced.  You might want to meet with these members in person and just talk about your cars and drive each others' cars to learn more about them.

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

[ja17]

Hello Niles,
Yes, it certainly sounds like your dealer does not know these cars.

It sounds like you have a basic accelerator linkage problem. You will need to review some of the many posts on "venturi switch" and "linkage adjustment". In addition "vacuum throttle control" and "constant speed solenoid" may also be relevant with your symptoms. You can use the search function.

Ask a lot of questions is the key here. There are a lot of owners who have ovecome these problems with the help from this list. Even if you do not do the work yourself, having the information on hand for your technician is always helpful.

Joe Alexander
Blacklick, Ohio

[TheEngineer]

If you want to know how these cars really should run & drive, come up to Seattle and drive mine. I have a lower ratio rear end. At freeway speeds it turns 3,000 RPM. Just right. It should run and shift smooooth about like a Lexus, but with a much firmer suspension. No jerks when shifting, except when you use kick-down. Write me e-mail.

'69 280SL,Signal Red,113044-12-007537,tired engineer, West-Seattle

[Cees Klumper]

Niles - that sort of behaviour is definitely not normal. Should be remediated for sure, as Joe Alexander points out, it could well have something to do with your linkages (sticking?) or constant speed solenoid.

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

[dldubois]

I had the same issue on my 69 automatic.  I initially thought it was idle related, then vacuum etc.  I ruled them out one by one.

Its in the shop now for the same issue as its really annoying.  My mechanic attributes it to modulator adjustment on the transmission.  I'm waiting to get the car back early next week and will report on his work as to what needed to be taken care of.

I've had the car in my family for 30 years and they definitely are not supposed to ride that way.



Dana DuBois

1969 280sl auto
blue (906)
Corinth, TX