As I recollect, the adjustment screw is a small trimpot in series with the 'ground' end of the potentiometer. It sets the lowest voltage output of the pot. It can be left where it is on the new pot, most likely.

The new pot should be installed in the same position as the old, initially. Use carefully scribed alignment marks to ensure this. The new pot should work just fine if installed this way, but if the voltage out at low idle is too high or low, it can be rotated SLIGHTLY to correct it. My feeling is that the voltage value you measured is acceptable and does not explain the problem. The behavior of that voltage at idle, and any instability of it, is what would cause a problem.

If slightly rotating the pot will not bring the idle voltage into range, reset its position by the alignment marks. Then try fine-tuning with the trimpot.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

An update: I installed the Air Flow Potentionmeter and warm start or hestitaion have not in improved. I set the voltage to 0.7v exactly on pin 2 to ground . The idle still has a slight hiccup 550-650rpm. When I am warm starting it, If I give it gas it will start and keep running unless I take my foot off the gas pedal. Typically have to keep on foot on the gas for 30 sec at least. I have not checked the voltage on the O2 sensor but the voltage read at pin 2 and 3 on X11 connector is running around 4.2 to 5V idle KOER. I am assuming that if the O2 sensors was bad my check engine light would be on and it is NOT. Any other ideas. I am trying to fix this before I put the car up For Sale.

Thanks

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Chris

2000 S500 (SOLD)
1985 300DT (CA model) 113K Miles (SOLD)
1989 300SE 47K miles (SOLD)
1998 VW Jetta MK3 TDI (Totaled)
2006 VW Jetta MK5 TDI

Kind of run out of MY scope of anecdotal experiences on our 190E. Our problem was erratic idle, sometimes falling so low as to stall, sometimes racing to 1200 rpm or more while warm. Besides the pot, I replaced ALL the rotting air plumbing rubber, including the south end of the airflow meter, cleaned the rotary idle valve, and resoldered the cold solder joints inside the OVP relay (better results than the new one I tried). Each step provided an incremental improvement, and idle as well as general running have been fine over a year since I took those steps.

Sounds like your situation is different - best of luck, and if you haven't taken all the steps I mentioned, perhaps my experience will in some way still be useful.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

This thread was very informative. Along withall the other things I have to do to my 300SE, I'm going to get a new pot.

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Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.