As I suspected, the Geo Metro air control valve did not move enough air for the m10 engine. So, I got a Ford style valve and installed it. Now the engine starts and idles as it should. Here are the details of my installation.
1. I made this steel bracket to mount the IAC under the first and second tubes of the intake. You'll note that I had to grind that nubbin down a little to clear the valve body:
2. Here is the Ford idle control valve mounted to the bracket. I have this thin wall tube that has an outer diameter that is exactly 16mm. I slid short lengths of it into the ports of the IAC and fixed them with Loctite 680 retaining compound:
3. I found a hose at the auto parts store, Gates #19047, that I was able to cut up to connect the valve and the inlet on the intake. Here is the lower section:
4. I made a flange from 1/4" aluminum plate with a bored hole and another length of that 16mm O.D. tube press fit into it:
5. Here is a shot of the upper hose. It is connected to the lower hose via yet another short length of the 16mm O.D. steel tubing:
This valve moves a lot of air, so the PWM duty cycle values for both start and idle are rather low.
That's it for this installment. There's not really anything left to do other than tune.