Skip the auto shop - Our mechanics make house calls

Q: I get a misfire on cylinder 4. After the car warms up it runs fine. Could it be plugs?

asked by on

When I start the car it runs rough and poorly. After a while I will shut it off and when I turn it back on it runs fine. What else could the issue be? I'm going to try new plugs today.

My car has 166000 miles.

A: As a general rule, car engines do not like ...

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・Save up to 30%

Get a quote

What others are asking

Q: Heater want stay hot

The lack of heat being generated by your system may indicate a clogged heater core. The [heater core]((https://www.yourmechanic.com/services/heater-is-not-working-inspection) is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this...

Q: Car shuts down when gas is pushed

Situations like the one you are experiencing are tough to diagnose with limited information because of all the variables involved. Things like low fuel pressure, or a large vacuum leak could cause a concern similar to what you are describing....

Q: It got really cold the next morning. I went to start my car and my belt will not turn. I drove it the day before the cold no problem.

Hi there. There could be a few things that could be going on. Either the battery was low on a charge or low on water and froze up causing the vehicle not to start up, or when the oil change...

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 Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
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.