Hrm.. I thought the computer used input from the coolant for the fan and a block temp sensor for the idle. Even if it kept the fan from coming on, it wouldn't be hard to wire the fan to come on whenever you threw the switch.
The car should be adjusting the mixture according to the MAF and the O2 sensor.. not just the TPS. That's all the IAC does is open a passage for air to bypass the TPS resulting in the high idle. But even so.. running lean at 2000rpm wouldn't really hurt anything, now would it?
:? I just don't know.
To my knowledge, the only sensor used by the ecu to turn on the fan is the ect. I personally never heard of a block temp sensor on an escort before (1.9, can't say for a 1.8 ). It would be rather easy to wire a switch into the fan circuit, but why if you don't have to. It would be just as much work to rig up a solenoid on the trottle and have everything run honky dory with no trouble.
The engine will run O.K.
without the tps connected (personally done it before), but it is rather unresponsive. Especially when load is applied, which is when it starts to run lean. I know that for an SPL comp it wouldn't be running lean for too long, but because of the load from the alternator, it would run lean. Why take that risk. Lean running engines tend to burn valves in a hurry, and can cause severe engine damage. Given the 1.9's record of dropping valve seats, it wouldn't help at all.
I like mikes idea. Don't know if an RC servo would be strong enough, but instead of powering a small RC servo, you could get the reciever to activate a relay to power a larger solenoid if required. Just make sure to put an off switch on the RC connection for daily driving, or some little kid playing with his car might take control of yours