Start up is fine when the weather is warm. The colder it gets the ruffer it runs at start until it warms up. The problem is in the the throttle body F.I. with a sensor or controler that controls the air fuel mix. In colder weather it needs a thicker mix of fuel.
There is a door in your air intake that is thermoststicly controlled
that is to remain partially closed until tge engine warms up.Thereby letting in cold air on a cold engine, causing it to run rough.
Testimonial: "Where is the door and what controls it? Actually what part do I need to replace?"
SOURCE: idle up and down to 1500 rpm at first start when cold
Have you by any chance taken a multimeter & tested your TP (throttle position) sensor ? If you think you might know how, let me know & we'll guide you through it. If not, at least take wiring plug off & clean both plug & TP sensor contacts with contact cleaner, and inspect for any corrosion while doing it. When putting plug back on, use a little di-electric grease in the connection. Have you sprayed your throttle body & throttle plate good with throttle body cleaner recently?
SOURCE: 1990 DODGE D150 WON'T START WHEN HOT
There is a temp. sensor on the exhaust manifold that I just switched out on car that done the same thing it would start when cold but once it was hot and you killed the car it would not start back. When this goes bad its throwing the wrong signal to the computer that it is too hot and allowing it not to crank. This sensor was on the left side of the engine if your facing the car from the front. Also It can be tested with a multimeter to see if it is bad.
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There is a much richer fuel mixture during a cold start, the colder the engine the richer the fuel mixture
retarded ignition timing causing the fuel to burn for a longer period of time makes the engine heat up faster
anything that doesn't allow the mixture to be properly metered, like vacuum leaks, bad temperature sensors, or O2 sensors, MAF or MAP sensors, bad EGR valves or PCV valves hoses or tubes,
and or
anything that will cause the fuel mixture not to burn properly, like worn spark plugs, or any other ignition part, wires, cap, rotor, timing, compression, will cause poor start or no start conditions that are worse in lower temperatures,
also low voltage, week battery, slow cranking of the engine can also cause hard to start conditions
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