[jkeyzer]

I have come to believe that the MFI thermostat is causing some of my troubles in getting my 2.4T MFI system set up. Recently I have been having a situation occur where even after running the car for 30+ mins, it will intermittently idle very rich, but then if I lean the idle out at other times it will be far too lean. I am starting to think that the warmup thermostat is not consistently and reliably engaging to the same spot, giving me some uncertainty in my overal mixture settings.

I get a small amount of hot air blowing through the thermostat, and all the hoses look ok although I do have a torn driver's side heat exchanger to flapper box hose. I have wondered if maybe there isn't enough backpressure on the heat exchanger air to get good airflow all the way to the thermostat.

In any case, removing the inspection cover and pushing on the control stub inside shows that there is still some movement left. The control stub is not pushed all the way to its stop by the thermostat, even when the car is warm. I haven't tried the propane torch/hairdryer test yet.

Has anyone tried modifying their thermostat to give it some kind of adjustability or to force it into a certain position for testing? I remember reading about threading a screw into it in the MFI articles and am curious if anyone has actually tried this. It would be great if I could get it to engage fully so that I can have more confidence that the mixture settings I am working on will "stay put". Beyond this maybe I could get rid of the flakey behavior by pushing it in further for a given temperature.

Any ideas welcome... I have a flapper box hose on order but I doubt that will fix the problem. (it will keep my toes warmer)