Crankshaft position & reference sensor tests

[911topdown]

The car is a 1984 Porsche 911 3.2 Carrera Cabriolet euro spec (i.e. no oxygen sensor or cat) and I am trying to resolve a slight hesitation under load at 2000 - 2300 rpm and low idle speed of approx. 650 rpm.

Before changing anything I decided to check the sensors and Idle Control Valve as per Bentley. The ICV is fine, vibrated with ignition on and the mechanism rotates when the unit is shaken. I checked the Cylinder Head Temperature sensor (bang on spec at 2.2kOms) and whilst I was there checked the crankshaft position sensor and reference sensor. The results were;
Reference sensor showed 1100 ohms between pins 1 & 2, open circuit between 1 & 3 and 2 & 3
Position Sensor showed open circuit between all pins i.e. 1 & 2, 1 & 3 and 2 & 3.

Bentley says both should be 650 ohms between 1 & 2 but it doesn't say what to do if it is open circuit. I would have thought that if either sensor was open circuit the car would not start and/or run like a dog but it starts on the button and pulls well throughout the range apart from the slight hesitation under load.

As it is working I am tempted to leave as it is and live with the hesitation but I don't want so suddenly find myself stranded somewhere.

Any advice?

Thanks

[wazzz]

There's a ref sensor and a speed sensor. Is that what you mean? That's the two black connectors under the white (CHT) one on the three-connector ramp on the left.

Bentley says between 0.6 and 1.6 kohms for both. Your 1100 measurement sounds good.
Forget about pin 3, it is the cable shield and it only gets connected to ground once the sensor is plugged back. No way to measure anything on it while sensor is unplugged.
If one of them is measuring open, you shouldn't be able to start car.
Once car is running you can unplug the ref sensor (not the speed sensor) and the car should keep running. But again, it should not start if no ref signal is given at start.

[911topdown]

HI Wazzz thank you for the response. Yes it is the speed sensor I am referring to. Your reply confirms that the car would not start if the speed sensor was open circuit so I think the best solution is to leave it as it is and look elsewhere for the hesitation and low idle speed. Strange that my digital multimeter can read the resistance of the temp and reference sensors but not the speed sensor (I did try different ranges on the tester).
I should have added that due to COVID lockdown here in the UK the car has not had a good long run for a couple of years but it was regularly started and run locally for 10 - 15 minutes to keep the oil circulated and get it up to temperature. I will check the plugs after a long run to see if there are any clues there.

[GH85Carrera]

The last time I had issues with running and dying I tested my sensors every possible way. In the end, the cure for my issue was replace them again. It was like a beam of light from the heavens, and angels sang, and my 911 ran like it is designed to again.

It is not always the sensors, but for me it was, for the second time.