Skip the auto shop - Our mechanics make house calls

Q: Vibration and high idle when i cold start it

asked by on

When i cold start my truck it has a high idle and vibration when rpm goes down

My car has 104000 miles.
My car has an automatic transmission.

A high idle upon cold start is generally normal for any vehicle as this is part of the cold start enrichment process as the engine warms up. As a general rule, car engines do not like cold weather and do not do operate as well in cold weather. When you start your car 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 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. 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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My car wont start the indicator show its on reverse but its on parking 2008 Nissan Xterra

Hi there - your symptoms suggest that the shifter cable has worn sufficiently to prevent proper gear selection, or has come loose from either the shifter or the transmission proper. I recommend a shifter inspection performed by a mobile, professional...

Q: 07 nitro overheating on me... water pump? thermostat? radiator cap? best way to diagnose

Hello. There can be a few possibilities that can cause the overheating condition. Have the radiator and pressure cap tested to make they hold pressure. Look for leaks at the water pump. The pump will show leak coming front the...

Q: Doesn't start when it is cold out

Hi, thanks for writing in. Electricity is heavily dependent on temperature and other atmospheric factors. Temperature being the most important. Most of the time this sort of problem occurs when the vehicle is hot though. Either way, the diagnosis is...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.