Car will not stay on.

My car will not stay on unless when I start it up, my foot is on the gas petal. Should I get new spark plugs or does this involve fuel pump? It also gave me a code of P0300.

My car has 215000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hi There,
Code P0300 relates to a cylinder misfire. Engine misfires can be caused by many different problems and are generally caused by either a spark or fuel issue or in some cases, a combination of both. Spark related problems generally will result from things like ignition coils, crankshaft position sensor, spark plugs, spark plug wires or ignition modules not working properly. When the misfire results from a fuel related issue, this is commonly related to a lean fuel condition (lack of sufficient fuel supply to the motor). Fuel related misfires can be caused by many different things such as low fuel pressure, faulty or dirty fuel injectors, a faulty O2 sensor, a dirty or failing mass air-flow sensor, a faulty or dirty idle air control valve or a vacuum or intake leak. When the fuel supplied to the combustion chamber is insufficient, this results in an ignition (spark) that is igniting a less than balanced load of fuel and air. This results in a misfire or an explosion in the cylinder that is much less powerful than the other cylinders. This creates a loss of power that resonates throughout the motor additionally causing other problems with ignition and fuel timing. Due to the number of different things that may cause an engine misfire, the quickest and easiest way to diagnose this type of problem is to hook the vehicle up to a scanning tool which will download any potential fault codes that may have registered in the vehicle’s computer as a result of the poor running condition. I would recommend having an expert from YourMechanic come to your location to diagnose your misfiring problem.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

About the Cadillac Deville Ignition Key Recall

GM has announced it is recalling 3.16 million vehicles due to a faulty ignition key design that can cause ignition switches to unintentionally move out of the “run” position. One of the vehicle models affected by that recall is the 2000-2005 Cadillac Deville.

The most common reasons a Cadillac CTS won`t start are a dead battery, an alternator problem, or failed starter.
The most common reasons a Cadillac DeVille won`t start are a dead battery, an alternator problem, or failed starter.
2005 DEVILLE UPHOLDS CADILLAC TRADITION

Breakthrough advances such as Night Vision, the acclaimed Northstar engine and StabiliTrak have shaped the DeVille`s character, distinguishing it from other full-size luxury nameplates.

If your vehicle won`t start, it`s usually caused by a dying or dead battery, loose or corroded connection cables, a bad alternator or an issue with the starter.
If the car cranks when you turn the key, but the engine won`t start, it could be because fuel isn`t getting to the engine. One potential reason for this could be dirty fuel injectors. Over time, the fuel injector nozzles can become clogged with rust, corrosion or debris.
The Cadillac Northstar 4.6 Liter engine was used in various Cadillac models from 1994 to 2011. Some of the models that used this engine during this period include: 1994-2005 Cadillac DeVille.
Capable of producing 300 hp (224 kW) out of its 4.6 L; 278.6 cu in (4,565 cc) displacement, the Northstar featured a cast aluminum 90° V8 block with 4 in (101.6 mm) bore spacing split into unitary upper and lower halves.
Base, DHS and Protection Series versions are equipped with Cadillac`s 275-horsepower, 4.6-liter Northstar V-8, while a 290-hp version of that engine is installed in the DTS.
Blown Fuse

If there has been a surge, a fuse that controls the fuel pump, the fuel injectors, or another component that`s vital for your car`s functioning, it may be the cause of your car`s failure to start.

Connected to the battery is the alternator, which works to generate power for your vehicle`s electrical components. When you have a brand-new battery but still can`t start the car, the alternator might be the issue. Cold and damp climates may increase wear on an alternator, causing it to fail.
If there is no sound when you turn the key, but the lights and accessories work, it could be the stater relay or starter solenoid. However if there is no sound at all, not even a click, it`s probably your battery.
When an engine cranks for a long time before it starts, either spark or fuel is missing or weak and each has its own reasons. Most of the time, the air / fuel mixture has been disturbed and there is too much air or not enough fuel.
The easiest way to perform an ECU reset is by removing the fuse from the fuse box. It is a very simple process, and all you have to do is pull out the car key, remove the fuse from the fuse box, and then put it back after about 15 to 20 seconds. Doing this clears any long-term memory stored in the car`s ECU.
MyCadillac Remote Start App

Convenience and control are well within reach using your MyCadillac Mobile App. No other luxury brand like Cadillac offers so many features. Users are particularly fond of the MyCadillac Remote Start capability, which enables you to start your vehicle right from your smartphone.

ECM stands for Engine Control Module, and ECU is short for Engine Control Unit. These two acronyms represent the same component and are used interchangeably.
If the ECM fuse keeps blowing, then there is a definite electrical short. Most of the time the short is in the ECM, but it may have a short in the wiring going to it. I usually isolate it by going through the wiring schematic and disconnecting areas of the circuit until I find the short.
Cadillac 4.2 liter twin-turbo V-8 LTA engine

The 4.2 liter V8 engine (GM RPO code LTA) is an eight-cylinder, dual overhead cam (DOHC) twin turbo engine produced by General Motors specifically for use in Cadillac luxury vehicles.

However, the complexity of Northstar engines meant they quickly became notorious for head gasket failures. And with the `Northstar Condition` affecting Northstar engines from 1993-2005, many owners can quickly find themselves facing costly repairs if these issues aren`t fixed quickly.
The 4.6L engine has a good reputation for reliability, but like any engine it has had a few problems. The relatively long timing chain that drives the overhead cams is tensioned by plastic guides on many of these engines.
The 4.6 L`s bore and stroke are nearly square at 3.552 in × 3.543 in (90.2 mm × 90.0 mm), respectively. Deck height for the 4.6 block is 8.937 in (227.0 mm) and connecting rod length is 5.933 in (150.7 mm) center to center, giving the 4.6 L a 1.67:1 rod to stroke ratio.
2005 DEVILLE UPHOLDS CADILLAC TRADITION

Breakthrough advances such as Night Vision, the acclaimed Northstar engine and StabiliTrak have shaped the DeVille`s character, distinguishing it from other full-size luxury nameplates.

The name “DeVille” is derived from the French de la ville or de ville meaning “of the town“.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

I put the wrong key in my car and a few weeks later my car just shut down and it will not start I believe it’s the computer but…
ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

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I just had my starter changed when I turned car on didn’t stay on. I had someone pass current and car turned on fine I drove car f
ANSWER : Hi there. It is quite possible that the starting issue you’re currently having with your Ford Focus is not related to the starter replacement. However, it could be due to might be due to your battery problem. When your battery does not have enough power to engage the starter, it also impacts other important systems critical to maintaining ignition, ranging from the ignition coils to fuel system components. It might be a good idea to have a professional mobile mechanic from our team come to your location to compete a car starts then dies inspection, so they can correctly diagnose this issue and ensure the right repairs are made.

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As I’m driving, all my lights inside/out of the car turn off and the car still stays on. But when I turn the car off it won’t turn over
ANSWER : Hello there. The charging system on the car may not be charging the battery as you drive and the systems that keep the engine running are priority so the engine will stay running until the voltage drops below about 9 volts but the lighting and some other accessories may cut off above this voltage first. You should have the charging system tested to see if the alternator needs to be replaced.

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Replaced alternator on car 2 times each time shows it’s charging 14v let car run for a little bit then test drive and car voltage
ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

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My car will not start Intermittently. I purchased a new battery 2 weeks ago and yesterday the car wouldn’t start. Got a jump and
ANSWER : The issue you are having is probably due to an intermittent fault in the starter motor itself or a deficiency in the starter electrical circuit, for example a large voltage drop due to a poor ground or a high resistance connection. These issues can be readily diagnosed and resolved on a mobile basis if you request a hard starting diagnostic. If you request that diagnostic, the responding certified mechanic will get this resolved for you promptly. Based on Toyota’s Factory Service Manual, the battery should not be disconnected if the vehicle engine is running. The battery acts as a large resistive voltage sink and consequently taking the battery out of the circuit, while the alternator is still running, can create a voltage spike on the car’s electrical system which is not good for voltage sensitive components such as the engine computer. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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Car dosent not stay on and it’s running very rich
ANSWER : The MAP sensor relies on the correct signals being sent to it. It is possible that the sensor itself may be working properly, but that the input signal to it may not be working properly. Try checking this along with the O2 sensor as well as this can also cause the car to run rich if it is picking up incorrect exhaust gases and making the wrong changes to the fuel mixture. If you need help pinpointing the fault, a certified professional from YourMechanic can come to your car’s location to diagnose the stalling problem and assist with repairs.

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Power steering loss, no belts are turning but the car is running fine. I also have a soft pedal. Whats wrong with my car?
ANSWER : I have only seen this situation once in my 30+ years and it turned out to be a broken crankshaft pulley. Belts are driven by the engine. The crankshaft pulley spins the belts, which in turn spin the air conditioner compressor, power steering and water pumps, and the alternator. The vehicle should be towed to your local repair shop and not driven. Without the water pump spinning to circulate the coolant, the engine will quickly overheat and result in more extensive damage.

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When I go to crank my car the key stays in the start position and the car is constantly trying to crank itself.
ANSWER : First, let’s make sure about some terminology before I proceed. I will assume the motor is actually turning over. If the car is trying to start, the motor has to be turning over or it is not trying to start. This is an important distinction when diagnosing the starting system. As a technician, I go to different parts of the system based on this description.

If the key is stuck in the start position, this is a ignition lock cylinder issue and the reason the starter continues to turn the motor over. If the starter is turning but the motor is not, then the starter is likely the problem. Either that or the teeth on the flex plate are all gone. This would require removing the transmission to repair.

If the car runs intermittently, this can be a big challenge. And it also means the starting system is working. It will need to be diagnosed when it is failing. A working car cannot be diagnosed because there is nothing wrong. Where you park your car should not have any affect. It certainly could be a wiring problem. Wiring problems hide really well and can happen anywhere in the miles of wires that are in your car. Isolating the system that is failing is really important here. At the moment I am unsure which system is failing. Starter system, ignition lock cylinder and or ignition switch electrical or something with the engine control system.

When the car is failing, you need to check for spark and fuel pressure. If neither is present, this is a clue. Usually the crank sensor will do this. Does your car have a tachometer? If so, does it move at all when cranking. This is a clue whether or not the cam and or crank sensor is working. Is there a Check Engine Light on with the key on? If there is a Check Engine Light, the code or codes can be used for specific diagnosis.

All of these concerns will send you down a diagnostic path. Be sure not to confuse yourself by misinterpreting multiple system failures. If the key does stick in the start position, this would be the first problem to solve. After that, does the motor actually turn when the starter turns? After that, the question of "Why won’t it start?" is first answered by finding what the motor is lacking. Fuel, spark etc… Good luck.

If you need assistance with these checks, contact a certified mechanic who has the tools and experience needed to properly diagnose this starting issue with your car.

Read Full Q/A … : Car will not stay on.