Misfiring when cold in 2002 Hyundai Accent

We have a 2002 Hyundai Accent that misfires when it's cold. If it's hot, it runs fine, but you can still feel a lag when you accelerate from the stop. We replaced fuel pressure regulator, filter and cleaned the injector.
Experienced mechanics share their insights in answering this question :
A lot of times, those noisy injectors flat and wear out when they get old and they need new injectors. What you want to do is have a mechanic, like one from YourMechanic, run a dealer-level scanner on it and analyze everything like the milliseconds in which the injectors are firing, the flow rate and all kinds of stuff that can be checked by a pro. You might need new injectors. That’s something that often wears out on these things. As old as it is, you might also have a wet and dry compression test on it, because if the engine is wearing out, the wet and dry compression will show it’s just flat wearing out and you just live with it. You probably are not going to want to rebuild the engine on it. It’s not worth it and it costs more money than the car is worth. Have your engine misfiring issue inspected by a certified technician, they will be able to recommend a repair so that you can get the most out of your car.

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What Causes an Engine Misfire When Cold? Direct fuel injection could cause a cold start misfire. With direct fuel injection, fuel does not touch the back of the intake valves. Since the gas and additives can`t clean the intake valves, carbon deposits can build on them.
Common reasons for this to happen:

Faulty spark plugs or wires. Faulty ignition coil. Broken piston rings.

From the spark plugs to the ignition coils, many different things can cause an engine to misfire. The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.
The injector may not be holding fuel pressure after the engine is shut off. When this occurrs with a hot engine the heat of the piston vaporizes the fuel. When the engine is cold the fuel sits in the cylinder and causes a misfire on start up until the cylinder clears its self.
The most sensitive parts of the engines are individual injectors. These are very narrow and can readily become blocked with small ice crystals. Diesel engines also have the added problem of the fuel thickening during cold weather. This makes it less free-flowing and can cause ignition problems.
Symptoms of a faulty cold start valve:

Engine stalling – After your engine starts, you may experience stalling while you drive. This will either occur at higher RPMs or when you take your foot off the pedal. Rough idle – Your engine may produce loud noises or even vibrations when you are idling.

What Does Code P0301 Mean? P0301 definition: Cylinder 1 misfire detected. Diagnosis: A misfire can be caused by anything from faulty spark plugs to low engine compression.
Ignition system components, including spark plugs, plug wires, ignition coils and ignition timing are culprits as are lean air/fuel mixtures and mechanical issues within the engine. Worn piston rings, worn or broken valves and worn cylinder walls, as well as worn cam lobes can also contribute to the problem.
Fortunately, you`re right about clogged fuel injectors being a symptom of a misfiring engine. If used correctly, though, a fuel injector cleaner should remedy the problem and stop your engine from misfiring.
A clogged or failed exhaust gas recirculation or crankcase ventilation valve or faulty oxygen sensor can send the wrong signals to the computer and cause misfires.
This could be caused by a cold state vacuum leak. Basically, this is a condition where a vacuum leak is present until the engine heats up and the induction parts expand and seal the leak. When the vacuum leak is present, you may be getting too much air, causing the engine to stumble.
An engine misfire can be temporary or continuous and will sometimes generate a check-engine code.
A thermotime switch, or TTS, is a sensor used to control the cold start enrichment process in some older fuel injection systems.
Start the engine and, using the procedure described in section 20, listen to the cold start injector (located on the air intake chamber). You should hear a clicking noise, meaning the injector is functioning. If a clicking sound is heard, let the engine reach operating temperature and repeat the check.
The most common sign of engine misfire is when the vehicle sputters and poor acceleration even when you step on the fuel peddle. This scenario is possible because when the engine misfires, sending vibrations you can feel while in the car.
What does the P0300 OBD-II code mean? When a P0300 trouble code is triggered, it indicates that misfiring occurs in random or multiple cylinders. This happens when there is a deficient amount of fuel being burned within a cylinder.
Code P0300 stands for “Random or Multiple Cylinder Misfire Detected.” This diagnostic trouble code (DTC) indicates that your car`s computer has detected an engine misfire that`s random and/or appearing on multiple cylinders.
Is it safe to drive with a P0301 code? You should not drive with a code P0301 set since a misfire can cause additional damage to your car. You should deal with the problem right away, taking the car to a mechanic. If the Check Engine Light is flashing, the car is dealing with severe cylinder misfiring.
Yes. While the damage may seem small initially, the longer you drive with a bad oxygen sensor, the worse the damage will become. Eventually, you may experience rough idling, poor acceleration, engine misfires, an illuminated check engine light, and failed emission tests.
A bad or faulty connected VVT solenoid can and often does cause engine knocking, inconsistent idle and acceleration problems. The issue could be with the solenoid itself or the electrical harness connected to the VVT.
As mentioned earlier, when the injectors become clogged, they lose their ability to supply the necessary amount of fuel or create a proper spray pattern, but worse yet, the corrosive nature of carbon deposits literally destroys fuel injectors over time.
The only guaranteed way to unclog a clogged injector properly is by removing the injectors from the engine. Once removed, the injectors can be dropped off or mailed to a professional injector cleaning service such as Injector RX.
If left untreated, a cylinder misfire can lead to significant engine damage. Worse, if you experience a bad misfire while driving, it could result in an accident. This is why it`s important to treat engine misfires as soon as you detect them.
Much like a slow-starting engine, misfires are caused by a coating of oil from leaky gaskets, grommets or O-rings. Give your plugs a once over, even minimal residue on single spark plug one is reason enough to replace them all.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Misfiring when cold in 2002 Hyundai Accent
ANSWER : A lot of times, those noisy injectors flat and wear out when they get old and they need new injectors. What you want to do is have a mechanic, like one from YourMechanic, run a dealer-level scanner on it and analyze everything like the milliseconds in which the injectors are firing, the flow rate and all kinds of stuff that can be checked by a pro. You might need new injectors. That’s something that often wears out on these things. As old as it is, you might also have a wet and dry compression test on it, because if the engine is wearing out, the wet and dry compression will show it’s just flat wearing out and you just live with it. You probably are not going to want to rebuild the engine on it. It’s not worth it and it costs more money than the car is worth. Have your engine misfiring issue inspected by a certified technician, they will be able to recommend a repair so that you can get the most out of your car.

07 Honda Odyssey. A/C will work sometimes. When working is ice cold. It will sometimes blow cold then warm and then cold again.
ANSWER : Hi there. In most cases, this problem is caused by air flow to the AC condenser. If you have a condenser that is clogged with bugs and dirt this could be the source of your problem as well. It is probably a good idea to have a professional mechanic come to your location to complete an AC is not working correctly inspection.

Will the front shocks and struts for a 1999 hyundai elantra fit on a 1999 hyundai accent?
ANSWER : Neither the strut assembly, nor the individual assembly components, for those two models in that year do NOT interchange in any parts catalogs and thus these parts cannot be interchanged on the two Hyundai models. YourMechanic can obtain the correct struts for your specific vehicle and professionally install them. If you desire that service, please request front strut replacement 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.

Cold engine misfire and hesitation – 1997 Dodge Dakota
ANSWER : Hi. I believe the ambient air temperature sensor, which measures the intake air temperature for engine management, has failed. It is reporting a far higher temperature than the engine is getting, as you have noted. Engine management is creating a leaner mixture for the engine than it really needs during cold start, so it misfires and has low power.

Replacing this sensor should improve cold start behavior. I would recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the car is hesitating and replace the air temperature sensor if needed.

My air is blowing cold-hot-cold-hot-cold-hot…
ANSWER : It is possible that you have a leak in the AC system. There are pressure switches that will turn off the compressor if the pressure is too high or too low. The low refrigerant level could cause the AC compressor to cycle on and off. If you would like to have this done, a certified technician from YourMechanic can come to your car’s location to diagnose the AC system and make the correct repair.

’14 Hyundai Accent oil is really muddy.
ANSWER : Unless there is obvious evidence of sludge, metallic particles, antifreeze contamination and so forth, the only way to judge oil condition is to send a sample to an oil analysis lab (there are quite a few out there for car owners; do a google search: "engine oil analysis lab"). Also, it is hard to judge your experience because I don’t know what your previous oil change intervals were. As far as reported complaints regarding Accent oil condition, I see zero. In fact, if you look at the 2014 Accent in the NHTSA database, there is an incredibly small number of complaints, indeed only 9 which, as I recall, is the smallest number I have ever seen on a 3 year old model of a fairly common car. Regarding the engine, there may be an ECM software update for your vehicle and you should check that (I see it in Hyundai’s TSB database). If the engine is not operating at full power, YourMechanic does offer a loss of power diagnostic and a certified mechanic could evaluate that for you and suggest any needed repairs. With regard to the steering wheel, the tie rod ends on left versus right may need to be adjusted in order to center the steering wheel. Too much cross camber can also cause the wheel to not be centered as you have to steer in one direction to keep the car going straight. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Random Misfire on Nissan Sentra
ANSWER : There are at least two recalls of the 2003 Sentra involving engine management issues. Consequently, you should first check your VIN at the NHTSA website to see if your vehicle is affected by any recalls. Carefully check the EGR system. If EGR is stuck open you can get global misfiring. Check the integrity of the PCV system, too. The fuel system needs to be ruled out including the mundane, but real, possibility that you have a tankful of bad gasoline. The actual fuel system pressure should be tested and verified against factory specifications. Injector operation should be verified. PCM failures that can account for global misfiring are rare but they do happen. It will be helpful to look at the engine operation using a real time scanner and also download freeze frame data from the misfiring episodes. If you want these diagnostic steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a misfiring diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

My car isn’t starting, it’s really cold out. I was wondering how can I start it with this cold weather
ANSWER : Hi there. Given the description of not being able to start your vehicle, when it is cold and jump starting the vehicle without any problem. This leads me to believe the battery does not have enough cold cranking amp capacity. The engine needs to turn over fast enough to start. This may be nothing more than a weak battery. I recommend having this confirmed by a certified technician from YourMechanic.