142 guy - what frequency for the IAC?
Oops, meant to include that. 92 hz.
For the OP, I was scrolling through my MS2 testing notes and found the results of some testing that I did in 2017 as part of refining my warm-up. These are the engine RPMs corresponding to the various points on the PWM output versus coolant temp curve during the warm-up cycle. I was tweaking the PWM to get the desired RPM as the coolant temperature was increasing during warm up.
Coolant temp 35C 45C 52C 57C
PWM 40.8 40.8 38.4 34
RPM 1290 1300 1130 950
Edit - the TB text editor suppresses blanks so I can't get the columns to line up - you will have to do that
These are all values with the car voltage varying between 13.9 and 14.1 volts. They will be different if the operating voltage is different on a 2 wire valve unless you have a perfect voltage sensitivity curve. They are also the settings for a B20E; but, they will give you an idea of what the values might look like.
MS2Extra has a voltage correction curve for the PWM valve. But, that voltage correction does not get applied to the PWM output until the engine transitions from cranking to running in the version of the firmware that I was using in 2017. Because the vehicle voltage during cranking will be low, typically 10 volts, you need to enter in large values of PW in the cranking PW versus temp curve. As the engine catches the voltage recovers and all of a sudden the idle air valve opening increases by a huge amount. As the engine speed crosses the crank-run transition RPM the voltage correction kicks in; but, the transition to the running PWM curve is not instantaneous so you inevitably get a big overshoot in RPM which complicates the cold start set up. I live where it gets cold. If you live where it never gets really cold the RPM overshoot may not be much of a problem. Hot restarts on my ca did not suffer this problem. I eventually fixed the problem by modifying the firmware to apply the voltage correction during cranking, recompiling the firmware and reloading it on my controller.
I used the 2 wire PWM because I picked it up for $5 Cdn in a pick and pull from a wrecked 940. It was the only European car in the yard so I didn't really get to choose. After all the work associated with tuning for voltage sensitivity and modifying and recompiling the code it would probably have been easier to spend the $ to buy a new 3 wire valve.
The other thing to be aware is that my valve was obviously used. Its a rotary valve and I noticed that even after cleaning mine exhibited some stiction. This resulted in the opening point for the valve varying about +/- 1.5% around 38% PW which complicates the tuning process. I see this stiction effect in operation during warm up. As the coolant temp increases and RPM drops the engine RPM will hang for a tiny bit and then drop 30 RPM in a step even though the PW output did not change. I don't know whether this occurs because my valve is old or whether that is the nature of the valve.
thank you this info has been helpful. The idle valve seems to be hunting a bit I suspect its my timing. Also I haven't been able to get it to start with no throttle, i'm not sure if its because i'm not giving enough fuel for cranking or or I need to adjust the throttle screw just a bit. As far as voltage is concerned I have a 200 amp alternator the keeps the battery pretty much always at a consistent 14.5v so I assume thats ideal for idle valve tunning?