Weird engine noise
1/11/16 | 05:05 AM
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Hearing a weird engine noise above 4000 rpm... At first thought it was an injector going out and the noise was a spark plug not being able to cause combustion but replaced the injectors and still causing the noise... It's very loud pinging noise... Anyone else having this issue??
Last edited by thatmustangguy89; 1/11/16 at 05:15 AM.
1/14/16 | 05:47 AM
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From: Clinton Tennessee
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Encyclopedia » Exhaust & Emissions » P0300 - OBD-II Trouble Code
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P0300 - OBD-II Trouble Code
Auto Systems and Repair
Random, Multiple Cylinder Misfire Detected
Our emissions expert has put together the following information about the P0300 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code
OBD II P0300
Fault Code Definition
Random, Multiple Misfire Detected
Symptoms
Check Engine Light flashing
Rough running, hesitation, and/or jerking when accelerating
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy
Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
Common Misdiagnoses
Fuel Injectors
Oxygen Sensor(s)
Powertrain/Drivetrain problems
Polluting Gases Expelled
HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog
Want to Learn More?
Generally, the term "misfire" refers to an incomplete combustion process inside the cylinder. When this becomes severe enough, the driver will feel a jerking action from the engine and/or powertrain. Often the owner will bring the vehicle into a shop complaining that the timing is "off." This is partially correct because a misfire does involve a mis-timed combustion event. However, the base ignition timing being out of adjustment is only one reason for a misfire to occur—and not the most likely.
P0301 Diagnostic Theory for Shops and Technicians
When the code P0300 is set in the Powertrain Computer, it means that the Misfire Monitor has detected more than a 2 percent variance in RPM between the firing of any two (or more) cylinders in the firing order. The Misfire Monitor constantly checks the rotational speed of the Crankshaft by counting the pulses of the Crankshaft Sensor. The Monitor wants to see a smooth increase or decrease in engine RPM.
If there are jerky and sudden changes in the speed output of the Crankshaft Sensor, the Misfire Monitor begins to count the RPM increase (or lack thereof) contributed by each cylinder. If it varies beyond 2 percent, the Monitor will set a P0300 code and illuminate the Check Engine Light. If there is more than a 10 percent variance, the Check Engine Light will blink or pulse in a steady manner to indicate that a harmful Catalytic Converter misfire is occurring.
When diagnosing a P0300 code, it is important to record the freeze frame information and then duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed because a P0300 (which is a specific misfire) can sometimes be difficult to detect. If the Engine System has a Misfire Counter for specific cylinders on the Scan Tool Data Stream, pay very close attention to the cylinders(s) named in the misfire code(s).
If there is not a Cylinder Misfire Counter, then you might have to switch components—such as coils, spark plugs, etc.—in order to isolate the root cause of the misfire. It is also important to note and record any other codes because the engine may be misfiring due to the failure or malfunction of another system or component.
Common Causes for an Engine Misfire and Code P0300
Ignition Misfire
An Ignition System problem is one of the most common reasons for an engine to misfire. As the spark plugs, ignition cables, distributor cap and rotor, and ignition coil wear over time, their ability to transfer the needed spark to ignite the air/fuel mixture inside the combustion chambers becomes compromised. In the early stages, the spark will only be weaker and the actual misfire will be subtle. As the ignition components continue to wear, the misfire will intensify and the combustion process can be interrupted completely. This will cause a severe jerk or shock in the operation of the engine (the engine may even backfire through the air intake system, producing a loud "pop").
Carefully inspect all of the Ignition System components for wear and heat damage. The Spark Plug terminals should have a sandy color and not be blackened with soot, white from an overheating combustion chamber, or greenish from coolant. Neither the Ignition Cables nor the Coil(s) should have any signs of arcing. If possible, Scope Check the Ignition System to ensure that the firing voltages are even—about 8 to 10 kilovolts per cylinder. If there is a Distributor on the engine, remove the Distributor Cap and Rotor. Inspect their terminals and contact points for wear, signs of arcing, and/or any buildup from corrosion. Though all ODB II vehicles have computer controlled timing, be sure to verify that it is within spec, even if it uses individual coils.
Lean Misfire
The lean misfire is another common reason for an engine "miss"—this is due to an imbalanced air/fuel ratio (too much air/too little fuel). Since an engine needs a richer (more fuel) mixture for a smooth idle, this problem may be more noticeable when the vehicle is idling. The lean misfire may decrease or disappear as the engine speed increases because the efficiency of the volumetric flow into the combustion chambers increases dramatically. This is one reason why a vehicle gets better mileage on the freeway than in the city. An EGR valve that is stuck open, a leaking Intake Manifold Gasket, a defective Mass Air Flow Sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire.
Pay very close attention to the Long Term Fuel Trim values because they indicate how much the Powertrain Computer is compensating for an imbalanced air/fuel ratio. If the Long Term Fuel Trim is over 10 percent on one bank of cylinders and not the other, there might be a vacuum leak or defective/cracked intake manifold on that specific bank. It is important to determine what is causing this amount of compensation. Check the Fuel Trim "numbers" over the full range of operating conditions. A healthy engine should have Long Term Fuel Trim numbers around 1 to 3 percent, either positive or negative.
Mechanical Misfire
Mechanical problems can also cause an engine to misfire. Common causes of a mechanical misfire are worn piston rings, valves, cylinder walls, or lobes on a camshaft; a leaking head gasket or intake manifold gasket; damaged or broken rocker arms; defective fuel injectors (and/or the electronics that control them); and a slipped or incorrectly-installed timing belt or timing chain. Generally, this type of misfire has more of a "thumping" feel to it. It is usually noticeable regardless of engine speed; in fact, it may even intensify as the engine speed increases.
A Compression Test and an engine idle Manifold Vacuum Test are two very important methods of determining the mechanical condition of the engine. Compression readings that are consistent (within 10 percent of each other), and at least 120 PSI per cylinder and a minimum of seventeen inches of steady vacuum, are required for reasonably smooth and complete combustion.
Powertrain Misfire
Sometimes, the engine has nothing to do with a misfire. One common cause for "jerky" performance that feels like a misfire is a problem in the transmission and its ability to properly up- or down-shift. If the misfire occurs during higher speeds, it could be a problem with the operation of the overdrive gear or a chattering clutch in the Lockup Torque Converter. If the vehicle jerks or feels like it is "missing" during deceleration, it could be due to harsh transmission downshifts, badly warped rotors, out of round brake drums, and/or sticking brake pads or brake shoes.
Vehicles can set misfire codes when badly warped and out of round rear brake drums violently jerk the entire powertrain when the vehicle slows from highway speeds. Make sure that you have the vehicle properly inspected in order to determine the root cause of the misfire. Entire engines have been replaced to solve a wrongly perceived mechanical misfire problem that was actually rooted in the transfer case, transmission, driveshaft, or front/rear differential.
Ask a Question
Find a Shop
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Encyclopedia » Exhaust & Emissions » P0300 - OBD-II Trouble Code
Q&A
Problem Reports
Recalls
Encyclopedia
Brakes
Drivetrain
Electrical & Lights
Engine
» Exhaust & Emissions
Heating & AC
Scheduled Maintenance
Suspension & Steering
Car Care Advice
Owners' Reviews
Blog
P0300 - OBD-II Trouble Code
Auto Systems and Repair
Random, Multiple Cylinder Misfire Detected
Our emissions expert has put together the following information about the P0300 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code
OBD II P0300
Fault Code Definition
Random, Multiple Misfire Detected
Symptoms
Check Engine Light flashing
Rough running, hesitation, and/or jerking when accelerating
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy
Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
Common Misdiagnoses
Fuel Injectors
Oxygen Sensor(s)
Powertrain/Drivetrain problems
Polluting Gases Expelled
HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog
Want to Learn More?
Generally, the term "misfire" refers to an incomplete combustion process inside the cylinder. When this becomes severe enough, the driver will feel a jerking action from the engine and/or powertrain. Often the owner will bring the vehicle into a shop complaining that the timing is "off." This is partially correct because a misfire does involve a mis-timed combustion event. However, the base ignition timing being out of adjustment is only one reason for a misfire to occur—and not the most likely.
P0301 Diagnostic Theory for Shops and Technicians
When the code P0300 is set in the Powertrain Computer, it means that the Misfire Monitor has detected more than a 2 percent variance in RPM between the firing of any two (or more) cylinders in the firing order. The Misfire Monitor constantly checks the rotational speed of the Crankshaft by counting the pulses of the Crankshaft Sensor. The Monitor wants to see a smooth increase or decrease in engine RPM.
If there are jerky and sudden changes in the speed output of the Crankshaft Sensor, the Misfire Monitor begins to count the RPM increase (or lack thereof) contributed by each cylinder. If it varies beyond 2 percent, the Monitor will set a P0300 code and illuminate the Check Engine Light. If there is more than a 10 percent variance, the Check Engine Light will blink or pulse in a steady manner to indicate that a harmful Catalytic Converter misfire is occurring.
When diagnosing a P0300 code, it is important to record the freeze frame information and then duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed because a P0300 (which is a specific misfire) can sometimes be difficult to detect. If the Engine System has a Misfire Counter for specific cylinders on the Scan Tool Data Stream, pay very close attention to the cylinders(s) named in the misfire code(s).
If there is not a Cylinder Misfire Counter, then you might have to switch components—such as coils, spark plugs, etc.—in order to isolate the root cause of the misfire. It is also important to note and record any other codes because the engine may be misfiring due to the failure or malfunction of another system or component.
Common Causes for an Engine Misfire and Code P0300
Ignition Misfire
An Ignition System problem is one of the most common reasons for an engine to misfire. As the spark plugs, ignition cables, distributor cap and rotor, and ignition coil wear over time, their ability to transfer the needed spark to ignite the air/fuel mixture inside the combustion chambers becomes compromised. In the early stages, the spark will only be weaker and the actual misfire will be subtle. As the ignition components continue to wear, the misfire will intensify and the combustion process can be interrupted completely. This will cause a severe jerk or shock in the operation of the engine (the engine may even backfire through the air intake system, producing a loud "pop").
Carefully inspect all of the Ignition System components for wear and heat damage. The Spark Plug terminals should have a sandy color and not be blackened with soot, white from an overheating combustion chamber, or greenish from coolant. Neither the Ignition Cables nor the Coil(s) should have any signs of arcing. If possible, Scope Check the Ignition System to ensure that the firing voltages are even—about 8 to 10 kilovolts per cylinder. If there is a Distributor on the engine, remove the Distributor Cap and Rotor. Inspect their terminals and contact points for wear, signs of arcing, and/or any buildup from corrosion. Though all ODB II vehicles have computer controlled timing, be sure to verify that it is within spec, even if it uses individual coils.
Lean Misfire
The lean misfire is another common reason for an engine "miss"—this is due to an imbalanced air/fuel ratio (too much air/too little fuel). Since an engine needs a richer (more fuel) mixture for a smooth idle, this problem may be more noticeable when the vehicle is idling. The lean misfire may decrease or disappear as the engine speed increases because the efficiency of the volumetric flow into the combustion chambers increases dramatically. This is one reason why a vehicle gets better mileage on the freeway than in the city. An EGR valve that is stuck open, a leaking Intake Manifold Gasket, a defective Mass Air Flow Sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire.
Pay very close attention to the Long Term Fuel Trim values because they indicate how much the Powertrain Computer is compensating for an imbalanced air/fuel ratio. If the Long Term Fuel Trim is over 10 percent on one bank of cylinders and not the other, there might be a vacuum leak or defective/cracked intake manifold on that specific bank. It is important to determine what is causing this amount of compensation. Check the Fuel Trim "numbers" over the full range of operating conditions. A healthy engine should have Long Term Fuel Trim numbers around 1 to 3 percent, either positive or negative.
Mechanical Misfire
Mechanical problems can also cause an engine to misfire. Common causes of a mechanical misfire are worn piston rings, valves, cylinder walls, or lobes on a camshaft; a leaking head gasket or intake manifold gasket; damaged or broken rocker arms; defective fuel injectors (and/or the electronics that control them); and a slipped or incorrectly-installed timing belt or timing chain. Generally, this type of misfire has more of a "thumping" feel to it. It is usually noticeable regardless of engine speed; in fact, it may even intensify as the engine speed increases.
A Compression Test and an engine idle Manifold Vacuum Test are two very important methods of determining the mechanical condition of the engine. Compression readings that are consistent (within 10 percent of each other), and at least 120 PSI per cylinder and a minimum of seventeen inches of steady vacuum, are required for reasonably smooth and complete combustion.
Powertrain Misfire
Sometimes, the engine has nothing to do with a misfire. One common cause for "jerky" performance that feels like a misfire is a problem in the transmission and its ability to properly up- or down-shift. If the misfire occurs during higher speeds, it could be a problem with the operation of the overdrive gear or a chattering clutch in the Lockup Torque Converter. If the vehicle jerks or feels like it is "missing" during deceleration, it could be due to harsh transmission downshifts, badly warped rotors, out of round brake drums, and/or sticking brake pads or brake shoes.
Vehicles can set misfire codes when badly warped and out of round rear brake drums violently jerk the entire powertrain when the vehicle slows from highway speeds. Make sure that you have the vehicle properly inspected in order to determine the root cause of the misfire. Entire engines have been replaced to solve a wrongly perceived mechanical misfire problem that was actually rooted in the transfer case, transmission, driveshaft, or front/rear differential.
Ask a Question
Find a Shop
Related Items:
random misfire
My check engine light is on and had diagnostic read random misfire but I just had all my coils and plugs replaced last April. What next?
Q&A > Ford > 2003 Ford Expedition
02 Sensor and Random Misfire
...ly and stalling. Ran code reader- codes 137, 141 and 0300. Replaced O2 sensor #2. still get random misfire and engine light came on after erasing codes. Ran code reader again, code 0300. What could i...
Q&A > Saturn > 2003 Saturn Ion
Random misfire need help
...sfire was showing I changed the plugs and still had the problem took it back and it is showing random misfire and 4 other codes one is my o2 sensor n the others r sensors I have the other codes if needed...
Q&A > Infiniti > 2003 Infiniti I35
P0300 Random misfire
...after driving for about 20 miles check engine light came back on check code same P0300 Random misfire
Q&A > Chevrolet > 1998 Chevrolet S10
P0300 Random misfire
...s reset after driving for about 20 miles check engine light came back on check code same P0300 Random misfire Answer #1 (0 ratings) Russ, February 11, 2009, 20:08 Can you feel the engine misfire? An...
Q&A > Chevrolet > 1998 Chevrolet S10
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How to Save Money on Car Insurance
Find out easy tricks to make sure you are not paying too much for your car insurance.
Buying Car Tires: When, Where, and How
Get these big-ticket items explained and know what tire-shoppers should look out for.
Should I Buy an Extended Warranty?
Find a plan that's right for you.
Ask a Question
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About Your Car
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Models: Honda Accord | Toyota Camry | Honda Civic | Acura TL | Toyota Corolla | Ford Taurus | Volkswagen Jetta | BMW 325i | Ford Explorer | Ford Escort
Auto Care Advice: Auto Basics | Common Problems | Hints & Tips | How To's | Lifestyle | Owners' Stories | Q&A | Recalls | References | Troubleshooting
Encyclopedia: Brakes | Drivetrain | Electrical & Lights | Engine | Exhaust & Emissions | Heating & AC | Scheduled Maintenance | Suspension & Steering
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