Could be a lot of things. My 190E goes to 1100 rpm as limp home mode when the EHA is unplugged or as in my case the Air flow meter pot is intermittant. With the EHA unplugged/not working/not controlled you won't get any cold mixture enrichment so the car will stall until it's warm enough to hold idle. Even when warm it will stay at 1100rpm as the idle valve is not being electronically controlled. I'm no expert at this but this has been my experience with my car. I can drive my KE jetronic 2.5 around with the EHA unplugged due to the broken AFM pot and it's fine, it will "cold start" - ie the valve shoots extra fuel initially - but it will die soon after until it gets just enough heat and throttle to keep an idle. After that it's fine. HTH in some way.