I own a 1988 300 e. I just had a new o2 sensor put in due to the code 5 that came on but now,code 4 came on. Accordong to my mech it is an AIRFLOW POSITION SENSOR or AIR FLOW POTENTIOMETER. The problem is I can't find the freakin thing anywhere.
Any directions please.

Remember what the K-Jetronics look like? They have that plate that moves up with the corresponding airflow (after the air has been filtered). You have a gadget like that...on the side you ought to see a connector, I believe that is what you are looking for.
Not sure if you can replace just it, or if you have to get a whole new kaboodle. If you do, it'll cost you $$

If I am wrong, someone please say so!

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

The actual potentiometer is not available from Mercedes but can be ordered through a Bosch distributor. The part number for your car is probably 3 437 224 035. Tricky part is adjusting it. Do a search on this forum for "potentiometer" and you will find lots of discussions.