The EPA emission certification test begins with a "cold start" at about 70 F. The amount of cranking and after start enrichment is minimum at this temperature, and it's been my experience that my car has poorer cold start behavior in the summer by sometimes stalling after firing up. Cold start behavior in cool weather is much better.

To work around this issue I just give it a little throttle as it fires and hold about 1200-1500 revs for two to three seconds. After that the idle stabilize at about 1000, and you're ready to drive off. This "problem" is not just limited to Mercs. A lot of cars exhibit similar behavior, and it probably results from the OEMs setting the cranking and after start enrichment to minimum levels. About 80 percent of the total EPA certification cycle emissions occur in the first two minutes of operation. This on a test that takes a total of about 45 minutes including a hot soak for about ten minutes, so the cold start enrichment in the vicinity of 70F is calibrated on the ragged edge of leaness.

Sometimes it's better for us to adapt to the car than trying the get the car to adapt to our preferences.

Duke

P.S. The following complaint is written on a 5/31/88 RO when my car was about four months old:

"Cust complains when starting at times it starts and dies"

They could note duplicate the problem, but wrote me the following NOTE: "All systems with EZL ignition system 5 seconds cranking time to start normal."