So, my '90 240DL is running very nicely, thank-you, but I'm having some idle speed problems. When the car is warm, it idles at around 1100 - 1200 RPM. When I come to a stop, the revs drop to almost nothing before rebounding right back up to about 1100. I'm getting the following fault codes:

2-3-1 Running rich or lean at cruise
2-3-2 Running rich or lean at idle
1-2-1 Faulty signal from mass airflow sensor

I did a thorough cleaning of the intake ducts, today, and the air filter is in good shape. I also cleaned the flame trap (neglected that for way to long, and it was pretty badly gunked up -- that alone netted me a nice increase in pickup, I think), but the codes came back.

So I suspect one of two things, and I wonder if I could get some other views on this. Perhaps the MAF sensor has gone bad. But another thing I noticed is that there are some cracks in the intake duct that runs from the MAF sensor to the throttle body. Clearly this is something I need to take care of, and if it fixes the issues, it would be a LOT cheaper than replacing the MAF sensor. So I'm wondering if a leaky duct on that side the MAF sensor sounds like something that might cause those codes and symptoms.

Cheers!
--EdM.
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'90 240DL Wagon 'Lola' -- '72 1800ES 'Galadriel'