Sounds like coolant temp sensor unpluged or bad(just a guess)
The coolant temp sensor is one of the computer inputs(major input for fuel metering)
ie. when the engine is cold it requires more fuel,when it is at operating
temp. it requires less fuel(just like a carburated engine has a choke)
If it is unpluged(or bad w/open circuit) the computer thinks it is 34f below!