I am coming into my second summer season driving and getting to know this beauty. It's parked all winter in a heated, but half basement garage.
The slight problem I am having is on cold starts in am.
When cranked the engine starts right away with no depression of the accelerator pedal but then it stumbles to a low idle and almost seems to stall but never does. After about 10-15 seconds of low rpm stumbling it perks up and runs perfectly. After the first start of the day it starts on half a crank and runs like a clock.
This weekend I used the car every day and the start scenairo improves but is still there.
I have also noticed that the problem seems grester in the warmer weather like now.
As I said the garage is half below grade and gets damp, especially when outsde temp is 75 and garage interior is at 55 and humid. Now I leave the doors open all the time and the moisture disppears. In these conditions I have to drive the car for a few miles before the hesitation and stumbling disappear.
-The warm weather problems seem to point to a moisture/electrical issue. -The winter stumbles seem to point to a poor cold start valve.
-Maybe the fuel is flowing back into the tank somehow when sitting a while?
The car was a florida car all it's life and was maintained to very high standards. It has 107,000 miles. The former owner installed all new points, plugs, wires, dist etc before I bought the car at 102,000 miles. Also the injectors were replaced at 95,000 miles.
Any insight on these M110 euro engines and their quirks would be appreciated. I have heard that that FI system was tempermental.
BTW, that engine is a tiger and becomes a different car over 4000 rpm's. Thanks
jz

Maybe I should have posted this to the SL forum.
I don't know how.

z:

From the symptoms that you describe, leanness would seem to be the most likely cause. The cold start valve provides enough extra fuel for a prompt start, however, when it shuts off the stumbling appears due to a lean mixture. Leanness can be caused by either high control pressure, or by the main mixture adjustment set too far to the lean side.

Control pressure is determined by the control pressure regulator, better known as the warm up regulator (WUR). If the fuel lines that connect to the WUR are partially blocked, the pressure will be too high until the engine is thoroughly warm.

The main mixture adjustment controls the mixture for all conditions of air flow, and is often set lean in an attempt to meet emissions limits.

Before chasing apparent injection faults, insure that the valve adjustment, cranking compression pressures, and ignition timing are all to specification.

Thank you Frank.
How long after start up does the cold start valve function?
A common cold start scenairo would be
- engine fires up then stumbles and coughs for ten seconds
- then engine runs smoothly but at low rpm's
- then after another 10 seconds or so the engine goes to what I believe to be it's higher rpm's that I would consider to be normal rpm's for a cold engine until the engine is warm. Then it settles down and runs perfectly.
Let me ask a dumb question:
What is the large screw adjustment on the right side of the engine below the front of the FI? It's a large white plastic flat head screw top with a slot. It seems to control air flow. I can turn it to adjust the idle speed.
Meanwhile I will take your advise and check pressures and timing. The valves were adjusted at 95,000 miles.
Again thanks for your reply.
jz

z:

The cold start valve remains on for only a couple of seconds post start.

The screw which you inquire about is actually on the left side of the engine. (a common error caused by facing towards the back of the car; irrespective of the direction of viewing, the left side of the car and engine remain the left side, and the right side remains the right side!!!) The screw, as you have discovered, is in fact the idle air screw, and does control idle speed. There is also a thermostatically controlled air bypass valve that provides extra air for warmup; if it is sticking closed it may also contribute to the symptoms you are experiencing.