Thats correct, it may not just be the cold start valve since you are having both cold start and warm start problem now. Check the fuel injection temperature sensor also. It is also called coolant temperature sensor. This sensor informs the computer about the temperature of the engine and based on the signal the computer adjusts the air/fuel artio. On my 87, 260E, this is the last sensor on the engine, towards the windshield. You can measure resistance on the sensor, when the engine is cold (20 deg-C), it should be between 2.5 and 3.5K and when it is at 80 deg-C, it should drop to between 250-350 ohms. The exact values may be different but when engine temp changes from 20 to 80 deg-c, the resistance should drop by a factor of 8 to 10.

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Saumil S. Patel