I replaced the pot in my '88 260e today and the car idles smooth as silk now - no surging or stalling.

Before replacing, I measured the resistance of the old and new pot (pin 1 to 3) and they were 4.07 k ohms and 4.06 k ohms respectively. I also measured the resistance of the trim pot terminals directly, 56.7 ohms old and 56.6 ohms new. Since they were so close, I did not adjust the trim pot.

The replacement pot has the 035 number and the shape of the wiper is a little different from the original 015. The new pot did not come with the rubber perimeter seal so I had to transfer that from the old one.

Aligning the pot on the air flow meter was easier than I thought it would be. I left the mounting screws slightly loose and hooked up a volt meter from the number 2 pin to ground. The car started and ran fine so I rotated the new part clockwise until the voltage dropped way down and the engine died. I turned it back counterclockwise until the voltage got up to about 7.5 volts and the engine surged and died. I ended up setting the alignment at .67 volts (actually it fluctuates between .64 and .69 and called it good.

Thanks everyone for all your help and input.

-John