Car does not start
My car has an automatic transmission.
This may be related to many different possibilities, some of which may be related to a lack of spark or possibly timing issues and some of which may be related to a fuel delivery problem or a combination of both. Things like ignition coils, crankshaft position sensor, spark plugs, spark plug wires or ignition module are all components that help to create spark and control ignition timing which may cause the motor to not produce spark or the correct timing needed to ignite the fuel in the motor.
In the case of a fuel delivery problem, this may be related to low fuel pressure, faulty or dirty fuel injectors, a faulty or dirty idle air control valve (this relays information about air intake to the computer which makes fuel adjustments), or potentially a faulty fuel pressure regulator or fuel pump. Fuel delivery problems will typically not allow the proper amount of fuel to be delivered to the cylinders which results in a lean fuel condition which can cause backfiring or simply cause the motor not to start as a result of fuel starvation. In some cases too much fuel may be supplied to the motor causing too much fuel to be introduced to the motor faster than what it can burn it. This results in the motor being flooded with too much fuel also causing it not to run properly. Any of the above possibilities can create an imbalance in the proper air/fuel ratio as well which will cause the motor to run very rough or not at all. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.
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Sometimes when you have problems starting an engine initially it is caused by a restriction in fuel flow; caused either by clogged fuel injectors or the throttle body that needs to be cleaned. Once the fuel starts to flow and engine warms up, it’s much easier to start. However, it could also be an air filter, EGR valve or other components that causes this issue as well, which is why it’s best to have a professional mobile mechanic complete a car is hard to start inspection so they can pinpoint the source of this issue.
At that point, it will use other methods to determine the fuel rate, such as pre-programmed fuel maps, throttle position, etc. I would suggest replacing the MAP sensor and retesting. If you would like to have it checked first, a certified technician from YourMechanic will be able to scan your vehicle and test components to determine the root cause of your starting issue before making a repair.
If you recently replaced your battery, the issue may be caused by a malfunctioning alternator or other electrical component that comprises the charging system on your Nissan Sentra. The best way to find out which item specifically is faulty, is to have a professional mobile mechanic complete a car is hard to start inspection. This will allow the mechanic to determine the precise source of what’s going on with your Sentra and recommend or complete the right repairs.
If your vehicle is under warranty, by law the dealer MUST repair the issue you are describing within a prescribed time frame and number of "attempts", otherwise the dealer will run afoul of Federal and state Lemon Laws that give you very specific rights, and recourse (contact an Attorney; we are Mechanics, NOT attorneys). Consequently, if the vehicle is still under warranty, to save yourself money do be sure to seek a resolution from the dealer. If the vehicle is not under warranty, obviously a certified Mechanic from YourMechanic could identify the electrical fault and resolve this for you. If you want to go that route, please simply request a no start diagnostic -electrical system and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.