How to fix bad cold starting VVT-i engine Toyota Corolla (2023)


How to fix bad cold starting VVT-i engine Toyota Corolla. Air flow sensor is dirty and I need to clean it.


Hello and welcome how are you doing today? I will show to you that if you have any issues or problems in your car starting and this cold it'll speed- and this means that when you try to start this car- and it is difficulties to start and expecially- if this little speed is too long or then then motor can suddenly shoot down in a cold.

Then it's good to check this, that this motors intake is full in extreme systems.

Intake air air air flow sensor and next I will show one example.

What in my Corolla has been- and this is this Toyota BB di engine and when ice, try to start and then notice that that this motor is now cold in here is this? Is this? Does this test port sing out that motor is cold and and when motor is hot and warm, then this is what is race away, but now I start to start this engine and what happened and this motor should dance, and sometimes it leaves in in model, is owned.

When I a little bit throttle this gas pedal and and 10-10-10 this model, when it warms, it start to run normally, but in that time or also this is this little speed is lower than 1000 and it's normally like 500, and if you have in this, this turned red in it'll, speed in a bomb model model or something like for 530 per minute.

Then it's good to clean this air air flow sensor and next vehicle to check that sensor, that what is this situation? Okay and we continue the spare filter folks, its vocation is just in here that area and next I will solve this.

You of that sensor and we change this picture.

Okay and the sensor is in trust in here then I take a closer view and its sense of area is in here and and what I need to do first, but I can look the stencil more carefully, because that is a I need to take this class without.

Why are out? There is a split, but it will be smooth and then next part is the terrorist one.

One is metallic.

Meat / I need to open here is the script better and then I use my screwdriver this way and then can I take.

Is this a proper that this intake robot out so that I've moved that you look at this way now it's out and then then I open this air filter where box is italic poking beams? Now it's open and then I take this carefully.

This is over then.

Here we have than this this sensor.

It is if their sense of location is here and then this small metallic, this pin what we need to press and when we press that down, despite the same same way that we pressed, we need a little bit move this this this part in tough area and that kind of program now leave this door open and interested aware again now it's open- and there is this cable, cable and I take different book again.

Now we now rejected at the sensor.

There was this cable and there is air filter, and here is the sensor, and now this sensor part is easy to open.

There are two crosshairs close to spot and I open up close, and so this is cruel, normal normal is crosshead cool, right click.

The second seems I need my house driver for fiver and I opened that sensor, hello.

There is this true pelvic and check is demoralized leg, this sense of how big a movement inside right, a little sense of vocation is I'm here.

This is the sensor, but this metallic part is the key element now I'll move that little bit and campus and sense or flower change.

That is so so bad focus and I need to open this, this port and then moving it and in the middle profit there was Hispanic metallic team.

Multi-Sensor goes away, and- and in here when we have the sense of their is critical- that this part must be very clear now when I looked at.

This part is totally in some kind of dusty, a small sand and now I need to clean that pot, and let next I will flee.

Okay and then I have here this.

This windshield washer fluid what is alcohol and then and I have here also this this cotton cloth.

What is in here and small screwdriver next I am planning to do so that that I I clean his part carefully.

His sensor, okay, now planto to clean this more sensor cause this part is dust and, and then he looked at in that side, it's clean, but this opposite side is totally.

Does this mean that my moles good private and then I have their basic? This means it also road and it's alcohol, then I is that this cap and I ride the road with this Boyd there's this cap I find very carefully to beat this alcohol, no alcohol antenna I.

Have this quote-unquote and I like I, take small heart small piece of this cotton and then I insert this cotton in this mud, alcohol cup and then I start the clean.

This sensor, okay- and this is interesting- first there's Madison cotton, and is this my clean cotton in there and then I move very carefully.

It's my small crew driver the same time, I clean that sensor.

It okay, let's see what is this.what white cotton sit Westland.

Yes, there is so much clean, so it is dirty dusty, then I take the part of this clean cotton.

I cut your small part of this copán and again in this alcohol, whatever Ilana and right again now, I clean is all parts in there inside in this, my my alcohol spirit, because trustee in Zara but and and there is very small gasket in here- rubber gasket pot I, like lean, also and then I change, this my cotton to totally dry, cotton and I take all of these alcohols away, and now, when we look this sensor part it is clean.

This is sensor, it is clean in there and that side is also in cleaning in there.

Okay- and this was this- was good information, and now we go to check that how this poor it'll works then- and we continue, can I install that sensor back in here and the sensor goes only one way: there's also this hole and now I out this time.

I need clean.

Also this over there is no really.

There is no any money any sound there, because this sound is back again and I clean.

Also this this inner aware there's no any sound here.

It is okay, okay, it's cool, that's cool down and then I instantly sensor sensor back and there is this.

So what goes in this hole? That's part goes in this direction.

A little bit move the it goes in, and then we checked it.

Okay, there's actually faulty this seal must go in inside okay and now, if this was cool check, this perv all sales, not okay, recruit that I check that and is school places here.

Two screws and I insert disk screws back earth, and this this one okay and then I rotate.

This goes back this code, then little bit more click them everything is fun and then sense of is fleeing in there it's ready, then I use the metallic click / italic clip in there.

This one takes this cable cast, cable and I, useless.

Okay, then, and I insert this is cover packing.

Here there are those holes per square.

It's okay here, just first answer comes again: they're intended host.

There is this small liner that this is the holes is in right position and then I pick them to focus in there and then I need to insert this cable.

What is in here this part- and it goes in this sensor sensor and let's go closer.

How goes first easy closed and I press B here? Ok, okay, now the split means that you can okay pull in here.

All right, then I checked this deal everything okay and why no check is the tie, start engine? Okay and next, when this sensor has been clean carefully and we have instant lead in pack, can we can check that? What is this bottles at the top is motor starts? Now and now this motor is again called a nice part and we check that out this model stuff.

Okay, looks good, and now this turns B is in normal in cold water.

It should be something like 1000 and 100.

It is normal speed.

Okay- and this was the speaks, and thank you for watching.


Where is the cold start sensor on a Toyota Corolla? ›

The cold start injector is also known as the cold start valve. The part is located on the cold air intake, which is found on the intake manifold.

What is the cause of hard starting for Toyota Corolla? ›

Fouled Plugs: Spark plugs create the spark which allows the vehicle to burn fuel. Fouled plugs are one of the most common reasons for a hard starting engine. As electrodes wear down, the voltage required to jump the gap to ignite the fuel increases. This can lead to prolonged cranking before the engine will start.

Why does my Toyota Corolla idle rough when its cold? ›

Engine Coolant Temperature (ECT) Sensor. One of the most common causes of rough idle on a cold engine is a faulty ECT sensor. This sensor signals the car's computer when the engine's coolant is cold or hot, so the computer delivers more or less fuel to the engine. A cold engine requires more fuel than a warmed engine.

Where is the cold start sensor located? ›

It is located under the throttle body on the lower intake manifold, right next to the ECU coolant temperature sensor (not the gauge temperature sensor).

How do you fix a cold start engine? ›

"Cycle" the Key. Make sure the radio, headlights, heater, etc., are switched to “off,” so they aren't pulling energy from your battery and engine. Now put the key in the ignition and turn it from the "off" to the "start" position about ten times. You're "cycling the key," which can help warm up the battery and starter.

How do you know if you have a bad cold start sensor? ›

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.

Why does my car struggle to start when its cold? ›

Your car may not start in cold weather because of problems in a number of areas. battery: cold temperatures affect the chemical process inside the battery and reduce its ability to hold a charge. alternator: alternator belts can become cracked in cold temperatures, making it more difficult to power your battery.

What sensors can cause a hard start? ›

Hard start symptoms and starter failure may NOT be caused by the starter, but could actually be caused by the crankshaft position sensor. If your vehicle is experiencing one or more of these symptoms, the crankshaft sensor may be at fault.

How do you fix rough idle? ›

How to fix it? Cleaning or replacing the fuel filter and adding a fuel injector cleaning treatment to the fuel tank should take care of clogged fuel injectors. If the rough idle persists, it's time to take your car to an auto repair shop.

What causes rough idle when starting car? ›

Dirty/Faulty Fuel Injectors – Fuel injection systems play an essential role in starting your vehicle. The system injects fuel and air into the cylinders. If clogged or gummed up, the injectors don't provide the right mix of fuel and air, resulting in a rough idle or slow acceleration.

Why does my car have a rough idle at start? ›

A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate.

What controls cold start idle? ›

When a cold engine is started, a component called the auxiliary fuel injector sprays additional fuel into the intake manifold. The extra fuel helps the engine start faster. But we also do not want the fuel-air mixture to be too rich. So, the throttle valve opens to raise the engine's idle speed.

How do you test a cold start solenoid? ›

To test that the solenoid is working, disconnect the wire connecting it to the starter solenoid and run 12 volts to the cold-start solenoid from another source. If you do not disconnect the starter wire, the starter will engage while the engine is running.

What are the two main sensor inputs for starting a cold engine? ›

These are the exhaust gas oxygen (O2 sensors) and knock sensors. The wideband exhaust gas oxygen sensor(s) tell the ECU the actual running air-fuel ratio of the engine.

What causes a cold start? ›

A cold start in an internal engine refers to the start of operation without the cooling water and/or oil having been preheated beforehand and without pressure having been built up in the lubricating oil circuit beforehand or without sufficient oil reserves in the bearing points.

Why does my engine stutter on cold start? ›

Beyond the MAF sensor, in most cases, an engine that stumbles when it's cold is caused by one of three different components: clogged fuel injectors, a dirty throttle body, or an EGR valve that is damaged or also dirty and needs to be cleaned.

What sensor would stop a car from starting? ›

One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn't working, the spark plugs won't fire, keeping the engine from starting.

What happens when a cold start injector is bad? ›

A leaky cold start injector may result in a reduction in engine performance and acceleration as a result of the disturbed air fuel ratio. In more severe cases, where a large amount of fuel is leaking into the manifold the vehicle may even experience stalling or misfires.

Would a faulty O2 sensor stop a car starting? ›

Yes, you can drive with a bad oxygen sensor if you can still start your engine and feel little difficulty driving. But don't leave it alone for over a couple of days, as it might cause safety problems and lead to the malfunction of other parts of your vehicle.

What is the most common engine starting problem? ›

A dead battery is the most common reason why engines fail to start up. A common reason for batteries to fail is drain. Your car's battery typically expends a small portion of its storage to start your car up, and then recharges from your alternator as you move.

How do you diagnose engine starting problems? ›

How do you troubleshoot starter problems?
  1. Look under the hood. Check the battery and battery cables to see whether everything's in working order. ...
  2. Tap the starter. Try lightly tapping the starter a few times with a hard object, making sure not to pound it. ...
  3. Adjust the transmission. ...
  4. Check the fuel gauge.
Apr 29, 2019

Why won't my Toyota Corolla start but cranks? ›

Most commonly, its caused by a fuel pump that's not working. The fuel pump fuse may have blown, or the fuel pump itself will need to be replaced. Alternatively, this problem could be caused by a leak in the fuel lines, clogged fuel injectors or a bad fuel pressure regulator.

What three sensors affect ignition timing? ›

A manifold vacuum and/or barometric pressure, throttle position, engine RPM, coolant temperature, and vehicle speed sensor all modify the timing program.

What are the three possible cranking system faults? ›

With a cranking system, symptoms are divided into one of three possible troubleshooting categories: Click — No-Crank (solenoid clicks but starter doesn't crank) No-Click — No-Crank (solenoid doesn't click/starter doesn't crank) Slow Crank (starter cranks, but engine RPM slow to start vehicle)

Why does my car crank a while before starting? ›

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.

What sensors can cause rough idle? ›

Oxygen (O2) sensor

An oxygen sensor monitors and analyzes the amount of oxygen in a vehicle's exhaust system after combustion. A dirty, damaged or malfunctioning O2 sensor (or sensors) affects the air/fuel mixture, causing the engine to idle rough.

What are signs of rough idle? ›

A rough idle may include any of the following:
  • Idling below or above its regular speed.
  • Inconsistent RPM.
  • Shaking or vibration through the car.
  • A skipping, slipping sound.

Will seafoam fix a rough idle? ›

SEA FOAM MOTOR TREATMENT is a fast, easy and low cost DIY fix for solving the most common causes of rough engine idle.

Is it OK to drive with a rough idle? ›

While it may seem like a small problem on its own, rough idling is a sign that some part of your engine isn't working properly. Over time, rough idling can result in poor gas mileage, starting issues and major engine problems.

Can spark plugs cause rough idle? ›

If your Spark Plugs are failing your engine will sound rough and jittery when running at idle. This can cause vibrations to resonate through the vehicle which could cause further costly damage.

Can low oil cause rough idle? ›

Oil changes keep your car engine running smoothly. Rough idling, slow acceleration, and engine noises mean you need to replace your car oil.

Why is my car idling rough and shaking? ›

One of the main reasons why your vehicle could be vibrating at idle could be due to worn out spark plugs. When a vehicle's spark plug is faulty, it can interfere with the air-fuel ratio leading to improperly firing cylinders, resulting in a misfire while idling. Replacing your spark plugs will solve this problem.

Why is my car idling rough for a few seconds? ›

Causes of a rough idle. Many different problems could result in a rough idle for your car or truck, including: dirty fuel injectors, clogged air filters, bad spark plugs, and a variety of exhaust system issues.

What is the most important sensor in a car? ›

Temperature sensor

Thermal management is crucial for the smooth running of a vehicle. Hence, it is one of the critical sensors in a car. The sensor is also responsible for the efficient functioning of the cooling system.

What are the sensors for the cold? ›

Cold is detected by specific thermoreceptor neurons that innervate the surface of the body.

Where is refrigerant temperature sensor? ›

The evaporator refrigerant temperature sensor extends vertically under the center of the evaporator. An electri- cal plug with four prongs is housed in the threaded end of the sensor, and is secured to the sensor with a black plastic nut.

Does coolant temp sensor affect starting? ›

A bad coolant temperature sensor may result in a lean fuel-air mixture, causing a difficult cold start.

What is the code P0420 on a Toyota Corolla? ›

What is a P0420 code? Simply put, a P0420 code means that the catalyst system efficiency of your car is below threshold (Bank 1). The P0420 error number indicates a low catalyst system efficiency. This is usually caused by issues with your vehicle's exhaust or fuel systems.

What happens when temperature sensor goes bad? ›

If the coolant temperature sensor malfunctions, it can transmit a false signal to the computer. And the response of the computer may unbalance the timing and fuel calculations. It is also common for a coolant temperature sensor to fail without warning and send permanently cold signals to the computer.

What sensor controls temperature? ›

The Thermocouple As A Temperature Sensor. The Thermocouple is by far the most commonly used type of all the temperature sensor types. Thermocouples are popular due to its simplicity, ease of use and their speed of response to changes in temperature, due mainly to their small size.

Can a bad coolant temp sensor cause rough idle? ›

The fault with a coolant sensor can manifest in two ways- A coolant temperature sensor that always reads cold may cause the fuel management system to mix fuel with less oxygen and waste fuel. On the other hand, a sensor that always reads hot can cause problems such as stalling, hick-ups, and rough idling.

How do I know if my evaporator temperature sensor is bad? ›

Symptoms of a Bad or Failing Evaporator Temperature Sensor (Switch) Common signs include lack of cold air coming from AC, temperature fluctuations, and the AC compressor not activating.

How do I fix my AC temperature sensor? ›

How to Fix the Air Conditioner Sensor
  1. Turn your air conditioner off as well as the power at the main electrical panel.
  2. Try accessing the evaporator coil inside. The sensor will be near the coil's location. If the sensor is bent, put it back into place cautiously.
Jul 23, 2021

Is there a fuse for coolant temperature sensor? ›

There will be a fused wire with voltage to the instrument cluster (your owners manual should indicate which fuse), but the temperature sensor is providing a variable "resistance to ground," which the temperature gauge in the dash is reflecting.

What sensors can cause a car not to start? ›

Bad Sensors

One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn't working, the spark plugs won't fire, keeping the engine from starting.

Can I drive with a bad coolant temp sensor? ›

If your coolant temperature sensor is failing or has failed, do not continue driving your vehicle. You should get it fixed right away. A faulty sensor can lead to overheating. This will cause damage to your engine as well as other components, which will be very expensive to fix.

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