Hi Reinhard,

Cold starts are great. On acceleration immediately after starting, the reaction is sluggish. As I said, if I rev the engin for a minute at 1500-2000 RPM, that sluggishness does not happen.

Once warm, the erratic idle kicks in, which could be O2 sensor related. However, now that the temperature is about 70, the problem is less pronounced. As the weather gets colder, the idle and overall performance greatly improve.

Obviously, some of this related to the fuel/air mixture. I already know I am running lean. And the cooler, denser, more oxygen-rich outside air is helping to compensate for that by apparently burning a limited fuel flow more thoroughly.

The O2 sensor is 4 years old. The (brass) fuel injectors could be original. I have never replaced them. Fuel filter is at least 3 years old. Fuel accumulator and pumps are probably original (I never had to replace them).

I noticed that since I implemented the 2 minute warm-up after each start, subsequent startups have been more immediate, even when the engine is hot. Then again, that could be related to the cooler weather we are experiencing.

DUKE: Saw the thread; sounds remarkbly similar to my problem(s)

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black