Shuddering , surging on startup

[450SEL1979]

I have a problem on startup of my recently acquired 1975 450SEL , rough idle and surging for 3 or 4 minutes until the car warms up a little. Also surging on coast , again only for first 5 minutes or so from startup. Any ideas ?
Forgot to add , I am currently trying some Wynns Injector cleaner in the hope that that might help
I am running it on premium unleaded 98

 

[Styria]

Hi 450SEL1979, it would appear that you are running the D-type fuel injection system on your car, and it is a system that I am not familiar with. Oscar, on his 350SE, runs the same injection system and you may wish to send him an e-mail or personal message as he has the system well sorted out. Let us know how you get on. If unsuccessful in contacting him, you may well have to consult the services of an experienced Mercedes mechanic and they are pretty thin on the ground nowadays. Regards Styria

N.B. Sorry I can't do better.

 

[450SEL1979]

Yes i am getting a liitle bit of an improvement after running a bottle of Wynns injector cleaner through a tank of about 50L . Will try taking it for a run on the expressway sitting on 110 for a good while. What i find is that after perhaps 4 or 5 mins it purrs along. Acclerates well and idles fine , just have that problem when started from cold. This is my 6th 450SEL , all up i have driven them for about 12- 13 years. Just have not come across this issue before. Distributor issue perhaps ??

 

[Oversize]

How often do you use the car? Could it be old fuel? Thermo switches are easily damaged through steam cleaning, so I'd check that the temperature sender for the computer is giving accurate signals. Sounds like she's trying to clear her throat, so it's likely the mixture during start-up is all wrong. It's more likely to be sensors, or injectors than anything in-between.

 

[450SEL1979]

Fuel shoud be Ok as i have filled her up with around 60 Litres 3 or 4 times since i bought the car. It is actually my daily driver. I do 4- 500K per week on average. Includes some M5 runs from Arncliffe to Horsley drive exit. Usually can get up to at least 80kmh , sometimes 110 depending on how heavy traffic is at the time. Have been told by my local merc mechanic in Alexandria that i should take it on a long freeway run after putting in another batch of injector cleaner. So may give that a go. City to Penrith and back may do it. Problem only appears when starting from cold in the morning .
. So injector/ sensor comments could be a pointer to the issue .
Once settled after that first rough running bit the car runs really well
I am curious to see if the warmer weather we are having at the moment make a difference.

 

[WiSeGuYY]

i'm not familier too about the topic but i can advise that the MERC workshop take a look and run checkup about electrical wiring and the spark ignition plus check the exhaust for the mixture out , ofcourse the injector nozzels too.

REGARDS.

TAREK

 

[450SEL1979]

i have run the injector cleaner through a tank of petrol. Had a few runs on the M5 at 100K + for a while. I am letting it run for about 2 mins in the morning before driving off , then try accelerating quickly if traffic permits.
Seems to be working as the shuddering/surging disappears quicker than a week or two back. Still yet to do that long run sitting on 110 that my mechanic recommended. He says after that a service , fuel filter change etc might get me there. We shall see if that is right.

 

[450SEL1979]

Problem solved !!
Car got to the point that it was surging erratically at low revs, cutting out as soon as i put it into reverse.Even cutting out as i braked in traffic on a down hill run. Not good with Sydney's "how close can i tail gate you " drivers.

So i handed her over to my local auto electrician for a day . he adjusted the injector firing settings and sorted the problem.$200 very well spent as far as i am concerned.Even the acceleration has improved . Surprising those idiots who pull into the merge lane and try and cut you off.

Will get exact details of what the auto electrician did and post them next week.

 

[Styria]

Brendan, that's great news and thank you indeed for bringing us up to date. Forgive me, if I don't recall readily, but you must have D-type injection. Correct ? I need to admit to not understanding how to 'adjust injector settings (I wasn't aware that the settings could be adjusted - not with K-Jet), thus I'd be most grateful if you could let us have further information on the work carried out by the Auto Electrician. Regards Styria

 

[Tony66_au]

75 it will be a D jet, As wel as what you have had done id suggest fuel and air filter as well, made a big difference with all my 450's and ironed out a few niggly issues.

Tony

 

[CraigS]

Good news that you have sorted the problem, but I would also have a look at what heat range plugs you are running.

 

[Helmet]

Brendan, that's great news and thank you indeed for bringing us up to date. Forgive me, if I don't recall readily, but you must have D-type injection. Correct ? I need to admit to not understanding how to 'adjust injector settings (I wasn't aware that the settings could be adjusted - not with K-Jet), thus I'd be most grateful if you could let us have further information on the work carried out by the Auto Electrician. Regards Styria

Sounds like they cleaned and adjusted the injection trigger points in the bottom of the distributor, pretty common