Well if fuel and spark are there, 'bout the only thing left is air
(or mixture) setting, right?
Dont know what FI your car has, but I've found with the CIS-E setups that a bad
sensor, faulty ground to the computer etc. can cause the FI computer to do
stupid things like, for example, tell the idle stabiliser to let the wrong
amount of air through. In this situation there's no way the car will start.
In the case of CIS-E you can actually disconnect the FI computer and then the
car will start (in limp home mode). Don't know if this applies to you though -
you say you have a frequency valve which means you probably have something other
than CIS-E. CIS probably??
To sum up, I suggest:
Check ground connections.
check wiring to computer from sensors (e.g. temperature).
check wiring from computer to actuators (e.g. idle control valve).
check sensors and actuators themselves.
See if you can start the car with various electronic things disconnected
(e.g. the brain).
The fact that the car was ok when you put it to bed, but wouldn't start
cold suggests a temperature dependant effect.
Another possibility is a vacuum leak - check the big rubber boot thing on the
Good luck, and let us all know what it was when you've fixed it.