It's been a long time since I posted any 'work' here. I rediscovered these pictures from about two years ago after a conversation with another Galant guy here. so I'm posting this thread to document the process.
This issue came to me as a colleague had a galant and he told me the car would not idle correctly. He'd been to a shop and they had screwed around with the idle screw and unplugged the throttle stop switch. I checked the ECU which had been capped about 6 months before and it was all fine. The idle screw was wound shut and when I logged the car I found the servo was hard over shut but still the idle was high.
Our cars have 4 methods for air to pass through the throttle body. all work together to make things good.
1/ throttle plate - driver uses this to control the airflow to the motor.
2/ idle screw - this is used to adjust the bypass air to the engine.
3/ servo - ecu uses this to finely adjust the air flow for smooth running
4/ fiav - this is the equivalent of the choke. at low temp it is open and allows air through (more air to go with more fuel for warm up).
The FIAV is under the knockout cover here:
When I took the servo module off the gap was huge so we did some experiments. The FIAV should close at about 90°C. So in a pan of hot water it went with a thermometer.
The valve did not close at all. Only option was to reset it all. Here is the valve disassembled:
Now as I had not done this before I was curious how much stroke I needed. so I put the thing in cold water and noted the position of the core poker. then we heated it again and noted the position. Poker is shown here (looking inside the FIAV that has been stripped):
After doing this I set the valve back (with a dab of sealant on the thread to hold it) and adjusted it so I could no longer blow through the servo body. Once I found this position I backed out the valve orifice (round bit with the thread on) approximately the same distance as I'd seen the poker move earlier.
Once this was done I verified the aperture was ok. We then heated the servo again to 90°C and verified I could not blow through the FIAV.
After that everything was reassembled and I reconnected the stop screw. We confirmed with the idle screw shut, it would slow, and with it open it was very fast. And also with the logger the servo was controlling open as the screw was closed and closed as the screw was opened.
I set up the logger and adjusted the idle screw so the servo was hovering around the middle of it's stroke after the car had warmed up. And it's been a doll ever since.
Hope this helps