450 SL in Denmark

Hi all,

I have now had the intake manifold and the valley cleaned which is nice in itself. In addition, all the lower rubber donuts have been renewed and so has the actual gaskets between the head and the manifold. 

Did it solve my running problem? Well, sort of. The car is indeed drivable and drives notably better. Smoother acceleration and a different shift pattern in the gearbox. Before, it would shift much sooner from 2nd to 3rd and now it goes naturally higher up the rev range before it shifts. It pulls evenly and steadily from 2000 upwards. From around 2000 rpm it runs beautifully. What is then the problem?

The problem is (still) that from 0 km/h and until the engine reaches 2000 rpm (no matter the gear), the engine stutters and there is intermediate "puffing" from the exhaust. It also smells of fuel. The idle is still rough and it smells of fuel. The idle screw on the ECU is turned all the way counter clockwise (i.e. lean). If I attempt to enrich the idle mixture, the engine reacts immediately and almost stalls.

So I have performed yet a new smoke test both with cold and warm engine and the conclusion is that it is tight (with a bellow on the throttle housing and opened flap). Only a slight trace of smoke from the throttle shaft and from two of the bolts for the cam covers. Hardly anything. I also measured engine vacuum which shows 680 mBar with hot engine. Prior to the renewal of intake gaskets and rubber, the vacuum was around 560 mBar. So clearly an improvement.

Any idea where to look? Can I still have a vacuum leak with 680 mBar idle vaccum?

Iginition timing is still on the mark and so is the fuel pressure (2 Bar). Dwell is smack on 30 degrees. 

Can the ECU be sending faulty signals to the injectors? Can something have happened with the MAP sensor? 

 





Best, Peter 

Hi Peter,
did you check the ignition timing following the instruction given by DB and noticed by Volker before?
It is really important especially in the lower engine rev's range.

I don't remember you reported having checked this in full.


Regards
Norbert 

Hi Peter,

I fully agree with Norbert. Ignition timing and its change over rpm and vacuum is something you should check well. I once had a 350 SLC of a friend and his igntion distributor timing would create the problems you describe now.

More than 600 mBar vacuum in idle is a good value.

Hi both,

Thanks to both of you for your patience and advice. I'll measure and adjust.
"DB"? - apologies if I'm being a bit slow here 

/Peter

Daimler-Benz

Natürlich