I just dealt with a similar problem on my 190DT. Your car has an idle control system, part of the EDS function. There are several key elements to the idle portion of this system:
- EDS computer
- Temperature sender
- Reference resistor
- Rack position sensor
- Rack solenoid
- Crank position sensor
Don't mess with your linkages unless you've done some basic maintenance on the electronics. The linkage isn't the cause of your grief. Here's what you should do:
1) read the "blink" codes. The procedure is in the FSM, and the codes vary somewhat from year to year. The reading can be taken with an LED, but I use this gadget:
Mercedes Diagnostic Code Reader Tool W124 Obd1 300e 320e 400e 190e and others | eBay
It's expensive for an LED, a switch and some wire, but it's all assembled and comes with a complete list of blink codes and diagrams. Saves time. If the codes suggest any faults, troubleshoot accordingly.
2) Clean the electrical contacts. The most likely problem is oil and dirt screwing up the solenoid or sensor at the injection pump:
A) The solenoid is a round gadget at the very back of the injection pump. Find the electrical connector and pull it out. Your manifold may get in the way, as mine did. Rather than remove the manifold, I worked it out with a very long pair of needle nose pliers. I then disassembled the connector enclosure, taking care not to break the plastic tabs, and this takes some effort. Then I thoroughly cleaned the pin bushings, and gave them a very slight oval with my pliers, so they would grip better. Sprayed the pins and bushings with Deoxit and reassembled.
B) The rack position sensor is located on top of the IP, forward of the ALDA. To get the connector out, you have to turn the collar counter-clockwise while pulling up on the connector. Work carefully, you DONT want to tear a wire. Don't try to take this connector apart, just spray inside the pin bushings with Deoxit, and also spray inside the well. Then reassemble.
3) The temperature sensor is usually one of the ones near the thermostat housing. Again, don't try to disassemble the connector, just clean it out with Deoxit.
4) The CPS is located on the left side of the bellhousing, and the wiring runs upwards and across. There is a connector in the middle of the run, open it and spray it.
If you've done this much, the system will almost certainly be working again.