1999 S-320 cold start-up problems

[jco24]

I live in Alaska far from a MB dealer. Last two winters my vehicle has been difficult to drive when below 45 degrees F. If I start and let it idle about 1-5 minutes (more the colder it is) it seems to run fine. But if I drive away too soon, it runs rough, has no power and backfires. It can be severe.

My local mechanic, an knowledgeable German car buff who drives his own older MB, says the computer shows no codes that he can use to identify the problem. Of course he doesn't have the more detailed chips as he sees too few MB to justify the expense.

The car is also going through spark plugs very quickly (less than one year til replacement needed).

I suspect the problem is some sensor that adjusts fuel-air mixture during colder conditions but don't have the knowledge where to start. I am facing a $2,000 bill (+ dealer charges) to barge this vehicle to Seattle and back, so it may be a reasonable choice to try changing a few likely suspect parts.

Any suggestions?