Q: Cold idle

asked by on February 08, 2017

on cold starts it will start fine. then after a few seconds the roms will fluctuate and it will sputter and i have to keep a constant idle with the gas pedal to keep it from stalling. it will also sound somewhat of like a small cam when it fluctuates. runs rich. exhaust pipes have black on them. very very cold starts not often though it will pop/misfire. after it warms up it will run fine for the rest of the day or until its cooled down for awhile but will still have slight gas smell even right after the truck is shut off but goes away after a short while maybe 10 minutes. white smoke will come out if i fluctuate the gas pedal after the cold start while its struggling to idle and the lights will go dim when the rpms are low and go to normal when rpms raise. will stall or try to die and rpms will fluctuate and will fuel surge if put in drive or reverse if not warmed up all the way after the cold start clears up after a half mile.

My car has 13000 miles.
My car has an automatic transmission.

What you are describing sounds the cold start enrichment process may be enrichening the fuel supply a bit too much. When you start your vehicle in the morning and turn the key to on, the coolant temperature sensor immediately reads the temperature of the coolant and relays this to the computer indicating that the coolant is cold. The computer then knows at this point that it needs to enrich (add more fuel) the air/fuel mixture at startup due to the change in air density. When you start the car, you will notice that it idles high for a period of time until the engine warms up. This is the enrichment cold start process. This is done with what is called a cold start injector or cold start valve which injects more fuel into the motor until the engine reaches a specific operating temperature. The computer simply feeds a little extra gas through the fuel injectors to start the engine and then maintains a certain amount of fuel supply to the motor until it is warm. In your case, it sounds like beyond this process there is an issue with correcting the air/fuel supply to an acceptable level that is not too much fuel given the temperature of the motor at that time. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle and diagnose your cold start issue.

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