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Gasoline engines need to be Choked when cold, colder it is the more "choke" is needed, fuel injection doesn't change that
Gasoline can not be ignited with a spark, yes the movie guys take liberties with that FACT, lol
Only gasoline VAPOR can be ignited by a spark
You know how gasoline really stinks in the summer, but you can barely smell it in winter, that's the VAPOR
Choke in this application means Richer fuel mix and higher idle
With a Carb you just needed a Choke Plate to restrict air flow into the top of the carb so more fuel was sucked out of the Jets, richer mix and a cam for idle screw, higher idle
Gasoline engine cylinders need 30% VAPOR to start
The colder the engine and gasoline, the more gas you need to add, if cold gasoline is 15% vapor then you need at least twice as much for start up
Fuel injection systems all have an ECT(engine coolant temp) sensor, added just for this purpose, 2 wire 5volt sensor, not to be confused with 12volt Temp sender used for dash board temp gauge, which has been around since the 1930's, lol
ECT sensor's temp reading tells the computer how much Choke is needed
So what you describe is possibly a failing ECT sensor, if it was bad(or unplugged) it would set a code, just failing it may show 60degF on cold start when its actually 40degF, so not enough choke, stumbling start and idle, but OK after warm up
The temp SENDER will have a red/white wire, and maybe a black/white wire
ECT sender a grey/red wire and a green/red wire
Both may have 2 wires in 1998, senders just had 1 wire until mid-1990s and the start of plastic engine parts, no grounds
Both are located at top front of 3.0l engine, usually near thermostat housing