Two problems started at the same time, they've got to be related.

At stop lights the idle will surge and if I'm not holding the brake hard enough the car will move, sometimes can be going 20mph at about 1300 RPM without touching the throttle.

If I turn on the cruise control it is erratic, like driving into waves of 70mph oncoming wind, constant pushing and pulling feeling and does make one sick.

Other than that, plenty of power and cruises the highway fine with manual foot control.

I was thinking the Idle Air Control Valve? Any opinions on that?

I need to fix this soon, because there is no way I'm driving 350 miles for Christmas without cruise control that does not make me sick.

__________________
1988 Mercedes-Benz 300E W124 M103 California Emissions/Controller

This may help you
http://www.peachparts.com/shopforum/diesel-discussion/123036-cruise-control-repair-articles.html#post883130



.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Most likely you are looking at a problem with the CIS-E fuel system that also controls the idle circuit.

The first step is to check the duty cycle.
Then disconnect the idle valve & see what happens.

__________________
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)
Retired Moderator