MFI Thermostat woes

[Luke]

Before I laid up my car for the winter, I noticed that my fuel consumption was, to be frank, terrible. Now I know this may have something to do with the weight of my left foot but I also think it has a lot to do with the MFI thermostat.

As I understand it the funky bi-metallic bits in the MFI thermostat are supposed to expand and flick a switch in the MFI unit to make it run more lean, however the feeder hose, coming from the heat exchanger up to the thermostat, never seems to get that hot (I appreciate it’s a 2 wall tube but I would have thought it would get hotter than it is).

I do not connect up my heating ducts as my car is only really driven in dry warm-ish conditions and as such I image I’m losing a lot of hot air out of the 2 heating hose connection ends of the heat exchanger, if I block these off, am I likely to get more heat through the MFI thermostat feeder tube and hence cure my fuel consumption problems? In doing so am I likely to screw up anything else? And finally, if this is feasible any tips on how to block off these large diameter holes (not welding)?

[Nick Moss]

I had this problem when the hose came off the heat exchanger. The car ran like s**t and blew loads of unburnt fuel out of the exhaust.
You can also get your symptons if the discs in the thermostat housing need cleaning, not a difficult job. You can test the thermostat by getting the motor hot, disconnect the tube and blow hot air in with a hair dryer.

[Luke]

thanks Nick I'll clean the disks (with carb cleaner and a toothbrush I assume) and see if that rectify's the problem.

[sithot]

You have to have your heater hoses connected to force the air through the system to the MFI thermostat.
To test this you can use a "heat gun" (hairdryer, etc) and aim it directly at your MFI thermostat intake. You should note a change in the way the engine runs once the thermostat kicks over.
Not having heater hoses connected defeats the purpose for the tube coming off of the heat exchanger.
Good luck.

Tom