Cold start acceleration hesitation

After the vehicle sits overnight cold engineduring idle, engine vibrates and after about a minute vibration's gone and comes back again a minute after - this cycle goes on and only stops when the engine becomes hot. When driving cold, i notice that the engine does not have enough power as before. It hesitates and shakes when going uphill. The hesitation and lack of power problem is gone once the engine becomes hot.

cold start acceleration hesitation

But even when its hot i can still say engine is running rough as compared to before. Hello There, 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. 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. Q: When cold, Engine shakes and hesitates during acceleration asked by Elmer J. My car has miles. My car has a manual transmission. Jeff Engstrom Automotive Mechanic. Thank Jeff.

cold start acceleration hesitation

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10 Causes of Car Engine Hesitation When Accelerating

Search forums. Hesitation and lack of power when cold. Thread starter rideapony Start date Jun 7, JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Hi all, I search for help regarding a hesitation and lack of power on my GT. I have a TFS and so far I've been troubleshooting this issue for a while. This hesitation and lack of power happens only when cold start after she reaches normal temp. Please help me finding what the heek is going on.

The only things left will be fuel filter, fuel pump, and maybe a vacuum leak? Only at cold start??? Mar 10, 27, 2, 74 Dublin GA lowendmac. Possible open circuit in the O2 sensor heater circuit.When you go to step on the gas pedal to accelerate, you will suddenly feel like the power has been lost in the engine for a couple of seconds.

Q: When cold, Engine shakes and hesitates during acceleration

Instead of going faster by stepping on the accelerator pedal, the speed will be reduced. The vehicle may even stumble entirely during these seconds. This is what it means when the car engine hesitates. It is usually the result of a problem with the air and fuel mixture within the combustion chamber. However, there is a long list of other reasons which could be the cause of this hesitation problem too. You will need to figure out the cause of this problem and get it fixed by an experienced mechanic.

In any case, you will likely find the problem relates to an imbalance in fuel and air mixing in the chamber. Either there will be too much air or fuel, or too little. To help you pinpoint the cause of this problem, below are 10 of the most common causes of engine hesitation while driving. This helps sustain the proper air and fuel mixture while the vehicle is in use. If this sensor goes badthe engine control unit will be unable to keep the right balance in the mixture.

Replacing the TPS is the only solution. If any of the vacuum hoses around your engine become damaged or worn out, you could experience air leakage from them. Then you will experience engine hesitation which is most noticeable at low RPM. Repair or replace any hoses which are causing the leak. This will cause your engine to lag, stumble, or hesitate.

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If there is a problem with your ignition systemsuch as with your spark plugs, rotor, or wires, then your engine will lose power at inconsistent times. This will cause hesitation as you accelerate. If you let your fuel injectors continue to be dirty, then it will impact how much fuel gets injected into the chamber. A good fuel injector cleaner is often a good, cheap fix that will restore proper fuel flow from the injectors.

The oxygen sensor is responsible for calculating the amount of oxygen that was not burned in the exhaust system. Based on this information, the engine control unit will know if there is too much or too little oxygen being ignited in the chamber. If the oxygen sensor is not working properly, then the proper air and fuel mixture cannot be achieved.

When outside air goes into the engine as part of the combustion process, the mass air flow MAF sensor measures how much of this air is going in.About one month ago I had a problem with some stuttering on acceleration a couple of minutes after starting the car. After that period of stuttering it runs great with no loss of acceleration.

It happens consistently each time I drive. I replaced distributor cap, rotor, wires, plugs and air filter and checked the timing normal with no change. I finally replaced the fuel filter and the problem seemed solved. Unfortunately, last week it started the same behavior again. The fuel pressure is normal during operation and with the fuel pressure regulator vacuum hose disconnected. The only thing I noticed is that the fuel pressure drops after I stop the engine.

Within about 5 minutes it is down to almost zero. Could this be causing these symptoms? I imagine fuel pump replacement is the solution. What do you think? Do you.

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Hi athiker, Thank you for the donation. The operating pressure is ok so it rules out a faulty fuel pump. It could be the pressure valve in the pump or a faulty pressure regulator. To test if it is the pressure regulator, pinch the return hose with a clamp and turn ignition switch ON to prime the pressure. If the time required is similar to without pinching the return hose. Then you need to check the fuel pump to rail for pressue leakages.

Sometimes it could be the hose from fuel pump to the mount that is leaking. You would have to remove the fuel pump to inspect. Was this answer. I clamped the return hose and the pressure held.

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I assume this means that I do not have any fuel leaking through the injectors or leaking out onto the ground. I think the fuel system is fine.Subject: 4. RE: 4. I had to get my pcm i think it was the pcm? Lead, follow, or get out of the way.

I would say that it is not a "death flash" but I cannot say for sure. When these flashes are performed nobody knows what changes they actually do to your PCM, not even the techs. Only the engineers and programmers know for sure. Since there has been little or no spark knock complaints about the 4.

As a tech, I wish I could actually alter the timing myself, but I can't. I guess if it doesn't bother you and does not get worse and you don't want to risk a possible "death flash" don't worry about it.

If it progressively gets worse, no flash will fix it and you have another problem and should have it looked at. If you're sure you've got all that stuff in good shape, and don't want to risk a flash that might retard your timing, you could bump your idle up a little. This is controled by a tamper resistant torx head screw adjusting the throttle blade stop. The correct tool should be availabe at parts stores, or you might do as I did - turn it by grabbing the exposed threads with needle nose pliers.

This should only be tried once everything else mentioned here has been checked. You shouldn't have to adjust it much. I have alot of torx bits, I believe its T I adjusted the "base" idle on my 3. I guess its no big deal, since its fine within driving for a block or so I just got a 4.

To assist with that they set the engine to stay in first gear longer to rev the engine up and not let you accelerate like it usually would. Is that what u are talking about or is it a different problem? Where the cam is positioned in the motor really has nothing to do with how long it takes to warm up. You accelaerate quicker in lower gears so the rest of what you read sounds like nonsense too. Where are you reading this stuff?

These symptoms are the first signs of a weak battery. The low battery will crank the motor but voltage goes low enough for the PCM to lose idle memory until the alternator brings the charge up.Eldon, Missouri Accelerator pumps. Often the accelerator pump gets the blame for other problems.

It is very easy to test the function of the accelerator pump. Start the engine, and warm to normal operating temperature. Shut off the engine. Remove the air cleaner. The choke butterfly should be fully open, as the engine is warm.

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Observe the pump jet in the carburetor, and with your hand, work the carburetor throttle to the wide-open position. You should observe a healthy squirt of fuel from the pump jet. A single barrel carburetor will normally squirt a single stream; while a two or four barrel carburetor will normally squirt 2 streams. If you see the stream s of fuel, the pump is working.

It is important to start the engine prior to doing this test. With modern gasoline, it is quite possible the carburetor will be completely dry prior to starting. If there is no gasoline in the bowl, the pump will not work; and this would give a false result. Bog, Hesitation, Stumble. This paragraph applies to an instantaneous bog, hesitation, or stumble upon acceleration. This paragraph also applies to relatively stock engines with the original carburetor.

We will discuss two types of bog: the first is bog when the vehicle is accelerated from a stop; the second is bog when the vehicle is accelerated from cruise. Most modern carburetors are designed to function with roughly 0.

cold start acceleration hesitation

This clearance allows for maximum velocity of idle air past the idle ports. Exceptions to this are GM carburetors with the idle speed air screw, and end carburetors on tripower.

Setting the idle for the highest vacuum idle reading will result in too little clearance of the throttle plate; forcing too much of the idle mixture through the lower idle port and too little through the idle transfer slot.

When the throttle is opened, there is now sufficient velocity of air to sweep all these droplets into the cylinders, creating a mixture which is too rich to burn, hence the bog. As soon as the overrich mixture is pumped out the tailpipe, and a normal mixture is ingested by the cylinders, the bog disappears. A defective advance mechanism can also cause bog; as can a defective accelerator pump.Home Articles Hesitation How to Fix a Hesitation Step by step guide on how to repair an engine hesitation when the throttle is depressed, this information pertains to all internal combustion engines.

Begin by parking the vehicle on level ground, in park with the emergency brake on. The engine will be running in many of these tests so use necessary safety precautions.

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Step 1 - If a malfunction has occurred that the computer has realized, the check engine or service engine soon light will be illuminated. First read the trouble codes and then define them to determine the repair needed. Many times an engine can hesitate without the computer detecting a problem, if this is the case proceed to the next step.

Code Reader Step 2 - Poor fuel pressure can cause the engine to go "lean" when the throttle is opened. The first check is to remove the fuel filter and check the flow by trying to blow through it, the filter should flow freely.

Fuel Filter Step 3 - The engine depends on a sealed system to contain vacuum the engine creates while running. If this vacuum system develops a leak it can cause the computer to react on false data resulting in a hesitation. Vacuum Leak Step 4 - The engine's fuel system must operate at a specific pressure, if this pressure is inadequate the engine will hesitate.

Cold start hesitation

Locate the fuel pressure test port or use a fuel filter adapter to connect a fuel pressure gauge and check the reading. Fuel Pressure Gauge Step 5 - The fuel system pressure regulator is designed to increase the fuel pressure when the throttle is depressed.

This pressure increase is used to enrich the fuel mixture when the engine is under load. Though some vehicles utilize an internal regulator located at the fuel pump in tank others are located at the engine fuel rail which can be tested much easier. Fuel Pressure Regulator Step 6 - The air intake to the engine is metered by a mass air flow sensor, this sensor provides feedback data to the computer which is then processed.

If this intake system is allowed to leak it will cause a misreading making the engine hesitate. Inspect the intake boot for tears or holes and replace if needed. Replacement Air Intake Boot Step 7 - The mass air flow sensor is used to measure the air that travels into the engine.

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Inside this sensor is a hot wire that becomes contaminated which inhibits its ability to provide correct information to the computer. If this sensor has more than 70, miles servicing the sensor can help cure engine hesitation. Service Mass Air Flow Sensor Step 8 - The throttle bore is designed to control the volume of air the engine will ingest. The butterfly and throat of the bore plate becomes contaminated with impurities and must be cleaned much like the mass air flow sensor.

Once this condition is corrected the engine can return to normal operation. Throttle Body Service Step 9 - The spark plugs of an engine are designed to ignite the fuel air mixture inside the combustion chamber to provide the engine's power. If these spark plugs or maladjusted or worn they can cause the ignition timing to change causing a hesitation, remove the spark plugs to inspect.

Spark Plug Step 10 - The clutch is designed to release the engine from the transmission, when this part wears it can cause a hesitation in the motion of the car. To test this condition drive the car at a steady speed, then very lightly tap the clutch pedal, if the car responds the clutch is worn. Step 11 - A timing belt or chain is used to keep the engine crankshaft to camshaft relationship correct. If this timing becomes misaligned, the engine can experience low power and hesitation.

Step 12 - A rare occurrence, but it does happen, if everything has not helped an engine hesitation and low power and the ignition system is suspect, remove the harmonic balancer to inspect the wood-ruff key. This key can become worn allowing the ignition trigger to become retarded causing the engine hesitation.

Hesitation Definition - An engine hesitation is an interruption of continuous power during acceleration. When a engine is hesitating it will cause the car to lunge or surge which will cause a sudden jerk as the car slows down.