190E idle cough after cold start.

Symptom:

Cold start is easy, but the idle is rough until car get warm. If press the pedal, the car cough seriously.

Step 1:

Turning the adjustment screw on distributor Clock wisely to richen the injection to see if the idle got improved. 
If yes go to next step.

Step 2:

Test Cold Start Valve (CSV), sent 12V power to CSV to see if you would hear a click from it. If yes the CSV coil works

Then:

Unplug Fuel Pump Relay, pin 4 is connected to Cold start valve. Attach a wire to pin 4, and re-install the relay. Start the engine when cold, send 12V power to CSV fitfully (force it to inject).

If more fuel made idle stable, this means your Post-Start Enrichment is not enough. Go to Step 3.

Step 3:

Remove the EHA on the distributor, turn the adjustment screw CW 1/4~1/2 turns. Re-install the EHA.

I solved my 190E rough idle problem. Car start immediately no matter cold or hot, and idle stable. Acceleration is smooth than before.  

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What I've Tried so Far but problem still exists:

Replace ECU, OVP , thermo-temperature switch

Clean IACV.
Clean ECU plug, Fuel Pump relay socket.