Dave, I've found that 90% of the time that problem is caused by the air-flow position sensor.
In fact I've had that problem on my street car & know that Benzmac also had the same problem.
Not a cheap OR easy repair
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)