AUTOMOTIVE FREAKS

If you diagnose a weak cylinder through an ignition scope or a digital storage oscilloscope (DSO), you’ll notice it sticks out like a sore thumb.

While each cylinder’s firing voltage will be displayed by the secondary parade pattern.

Cylinder number one will be displayed on the first place, and it will be followed by the rest other cylinders from left to right according to their firing order.

When you notice that the peak firing voltage for a certain cylinder is unusually higher or lower than the rest of them, you have your suspect, this is the cylinder that indicates problem.

If the firing voltage is lower than others, it may indicate that the spark is finding a shortcut to the ground. There are many possibilities that may create such condition:

• A cracked, shorted, faulty spark plug.
• Uncovered spark plug wire.
• Spark plug electrode is too badly worn or too wide.

If you observe during the engine idling that the firing voltages of all the cylinders are relatively equal, you may perform a snap-kV test.

This test can help you discover a misfire that happens during engine under load condition.

In order to perform such test, you need to observe the firing pattern on the scope by suddenly opening the throttle wide and then let it fall back.

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If everything is normal during the snap-kV test, all the firing voltages should increase.

But if there’s one or more cylinders that increase significantly more or less than the rest, you should check them because this is a trouble indication.

If you find a higher snap-kV voltage spike than others, it points to high resistance in the ignition secondary to the affected cylinder.

When this happens you may want to check for an open or excessive resistance in the plug wire.

If you encounter a spike that’s shorter than the others, it may point to loss of voltage.

To overcome this problem, you should check for a damaged, cracked, or shorted spark plug. You may also want to check for a shorted plug wire or arcing across the broken spark plug.

There is also a case when misfire happens under load and all spike heights are low during the snap-kV detection.

This condition indicates that coil’s voltage is low. The situation is most likely caused by a damaged ignition coil.

But you should also consider the possibility of low battery voltage, because it can also produce similar symptoms. So you also need to test the battery and charging voltage.

ACCEL 140012 EEC-IV Supercoil

Okay, now the next thing you need to observe is the primary pattern for the suspected cylinder.

By observing the primary pattern you can discover additional pieces in the diagnostic puzzle.

You will gather important information from the primary pattern such as :

• The peak or “arc-over” firing voltage. (This info is already observed and determined as lower or higher than usual by you).

• When the coil starts to charge

• “Spark burn line”

• Coil oscillations.

As a part of the waveform, the spark burn line immediately follows the spike of firing voltage.

By observing the height of spark burn line you can retrieve information about air/fuel mixture.

If you notice the spark burn line is taller than normal, then the fuel mixture is running lean.

When the air/fuel concentration is rich, you’ll notice that the line is lower than normal.

There are several situations that can cause lean mixture in a single cylinder :

• Air leakage past injector O-rings.

• A leaky intake manifold gasket

• A leaky EGR valve. This may happen if the location of the valve is adjacent to the cylinder intake port.

• A dirty, plugged, or inoperative fuel injector.

• A leaky head gasket

• A leaky (burned) exhaust valve

A leaky (burned) exhaust valve or a leaky head gasket may lead to loss of compression. This condition may affect the spark burn line to behave the same way.

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If you experience all the spark burn lines of the cylinders are higher than they should be, then you should find out the underlying problem that affects all cylinders.

The underlying problem can be one these conditions:

• A weak fuel pump or damaged pressure regulator that leads to low fuel pressure.

• A Leaky vacuum hose

• An intake manifold vacuum leak

• A Leaky EGR valve

• A leaky throttle gasket

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Beck Arnley 039-5030 Throttle Body Gasket

There is a quite rare case where a rich fuel mixture is detected in an individual cylinder, this may be caused by a leaky fuel injector.

A rich fuel mixture in all cylinders is a more common condition found on engines.

The problem is usually caused by a damaged coolant sensor or oxygen sensor.

This situation tricks the computer and prevents it from going into closed loop.

A damaged fuel pressure regulator that forces excessive pressure to the injectors may also cause this problem.

There is one more thing that you may want to look at in the spark burn line. It’s the amount of “hash” the spark burn line shows.

If the cylinder is in a good condition, it will display a relatively clean line with little hash.

However you’ll find a lot of hash if the cylinder suffer from ignition misfire or lean misfire.

You’ll discover more clues about what’s going on inside the cylinder by observing the length or duration of the spark burn line.

If you observe that the spark burn line duration is longer than about 2 milliseconds, it means the air/fuel mixture in the engine is running too rich.

While the shorter burn line indicates that the cylinder is running abnormally lean. The burn line is considered short if it’s shorter than about 0.75 milliseconds.

Coil oscillations, this is the last thing you should observe. The coil may be considered as in good condition if there are at least two or preferably three or more oscillations that take place after the spark burn line.

If the oscillations is less than two, it may indicate a damaged or weak coil.

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Digital Storage Oscilloscopes

Photo by Honda CB77 Restoration Isolating the misfiring cylinder is the first step you should do in diagnosing a steady misfire.

There’s an old schooled method that requires you to temporarily disconnect each spark plug wire, one at a time. You should do this while the engine is idling.

If you notice that there’s no change in the idle speed when you remove a certain spark plug wire, then you have found the trouble maker, this is the weak cylinder.

You may also perform a power balance test that can show you the same thing. But in order to perform this check you’ll need some hookups and an engine analyzer.

However doing a power balance test is far more convenient because you don’t need to deal with those wires thus preventing you from electricity voltage.

It also avoids you from causing any damage to electronic parts of the ignition system.

You should be extra careful when you decide to disconnect the plug wire from a spark plug.

Because when you do that, the high voltage surge from the coil isn’t able to flow through its normal path to the ground. What it does is flow back through the coil.

Automotive Digital Multimeter

Most ignition systems are created to be strong enough to hold such voltage backups intermittenly. But most of them aren’t designed to withstand the voltage for a long term.

Especially when the ignition module or the coil is already in a weak condition, the surge may force the component over the brink that eventually lead it to failure.

So you should make sure that you don’t disconnect the plug wire from the spark plug for such a long time.

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Check Engine light will illuminate and the scan tool will produce a P-code that is relevant to the misfiring cylinder when OBD II system traces/analyzes a misfire problem that’s beyond “normal” thresholds.

By reading the last number of P0300 series misfiring code, you will know which cylinder that has the misfire problem.

For example a code P0304 means misfiring problem occurs on cylinder number four.

Unfortunately, you have no idea what causes the cylinder to misfire since the code doesn’t provide such information. The problem may be caused whether by compression, fuel, or ignition.

However if you also read a P0204 code then the misfire problem may be caused by a damaged injector. Because the P0200 series codes are related to injectors.

Photo by EMSL If you find any EGR codes from the reading, for example the code is P0401, the misfiring problem may be the result of carbon buildup under the valve of EGR.

There are also lean codes, they are P0171 and P0174. If the scanner reads one of these codes, dirty fuel injector could be the cause of the problem.

Now, if what you get is nothing but the misfire code, I recommend you to check the ignition components of the cylinder.

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Remember as I’ve told you before check the cylinder that corresponds to the last number of the code.

In this case, there are several possibilities that can cause the problem, they may be:

• Fouled spark plug

• Badly worn spark plug

• Carbon tracking

• Bad plug wire

• Defective or weak coil in a multi-coil distributorless ignition system

• There’s moisture inside the boot of a coil-on-plug ignition coil

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If your OBD II scanner pulls P0300 codes randomly, then the misfire is random and it moves around from cylinder to cylinder.

It is usually caused by something that disrupts the balance of air/fuel mixture.

That something can be a leaky EGR valve, a major vacuum leak, or sometimes a low pressure condition.

Such low pressure condition may be caused by a faulty pressure regulator or weak pump.

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http://www.metacafe.com/watch/yt-_q7yEMwP96U/

The video above explains how misfire happens, it provides the animation that helps you better understand. Watch and Learn more

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Photo by SportscarWorkshops Depend on the cause of the problem, misfire is a common issue that’s not always easy to trace.

When a misfiring cylinder happens on your four cylinder engine, it is hard to ignore. If the engine loses 25% of its power, it would be like a horse that tries to run only with its three legs.

You’ll find the engine shakes so badly when it’s on idle. The vibrations are so obvious that you may feel them from the steering wheel and throughout the rest of the car.

Depending on the accessory load of your vehicle, you may find it hard to start the engine and it also may stall at idle.

The accessory load of your vehicle is usually comprised of air conditioning, electric rear defroster, headlights, etc.

Your engine’s performance, fuel economy, emissions and even idle quality, they all will decline due to misfire.

Because of the unusual high levels of hydrocarbons concentration in the exhaust, your car will most likely fail an emissions test.

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Now let’s face the one million dollar question, “What causes a cylinder to misfire ?”

There are basically three things that can generate this problem:

1. No spark. Yes it’s just like human relationship (Just kidding).

Loss of spark may happen when there’s a condition or thing that prevents coil voltage from jumping the electrode gap that’s located at the end of the spark plug.

This situation may be caused by worn out, damaged, or fouled spark plugs.

A cracked or bad spark plug wires may also be the source of problem.

If there’s excessive rotor gas inside a distributor or a weak coil. This will affect not just a single cylinder but all of them.

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2. “Lean misfire” This situation may occur when there’s not enough gasoline in the air/fuel mixture. There are several things that may be responsible for such condition.

This can be caused by :

- An unresponsive, dirty or clogged fuel injector.

- Air leaks.

- Weak pump that causes low fuel pressure.

- Leaky pressure regulator.

- Restricted filter

If the low fuel pressure or air leaks are the cause, all cylinders will be affected.

If there are any leaks on EGR valve the effect will be similar to an air leak.

The fault will most likely be carbon buildup under the EGR valve, if your vehicle generates misfire code of P030X and a P0401 EGR code.

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3. Loss of compression. This situation happens when one or more cylinders lose most of air/fuel mixture before it is able to be ignited.

The main suspect for this case is a blown head gasket or leaky (burned) exhaust valve

If you experience misfiring on two adjacent cylinders, the head gasket between them may have failed.

If your engine experiences overheating or it loses coolant, then it may be caused by the head gasket too.

Many mechanics will tell you that Intermittent misfires are the hardest problem to trace.

This is true since the misfire may appear and go depending on operating conditions or the load of the engine.

The misfires seem to occur without any obvious reasons.

When the engine is cold the engine may misfire and run rough but after warming up, the engine begins to smooth out.

It may also run good for most of the time but without any apparent reasons it may suddenly cut out or misfire.

Another symptom is the engine may run smooth during starting and idle but the engine begins to misfire after coming under load.

http://www.metacafe.com/watch/yt-zHKczFZcXwA/

Watch the video and learn how this expert teaches you the basics techniques to detect / diagnose a misfire.

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Photo by follettmotors_com One of the most expensive parts of a car to replace is catalytic converter. Perhaps this is the reason why you read this article.

You’re not alone because many people actually try to repair the converter on their own in order to cut down the cost.

In order to perform the task, a general knowledge about automobile and exhaust systems are required.

If you feel like you have a doubt of doing it yourself, it will be better to take it to an experienced mechanic.

However if you believe that you have the courage to do it and are willing to upgrade your knowledge about emissions and exhaust systems, then feel free to scroll down to end of this post and check out several similar articles on this site.

These articles are related to emission systems.

When you’ve learned the basics, you’ll gain the courage and feel more comfortable to start working on your own.

But before we continue, let’s prepare a few tools that will be required to perform this task.

• New Catalytic Converter

• Ramps

• O2 wrench

How To:

1. You need to lift your vehicle. The catalytic converter is located in the middle of the bottom part of your car.

Because it sits somewhat in the midway down of the length of your vehicle, you can’t reach the converter by only lifting one end or the other.

When working from home, ramps will be your best tool to help you reach the parts.

Actually, this can be considered as the most difficult part during the replacement process.

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2. Handle the bolts with patience, sometimes due to their size and improper placement, those bolts are hard to remove.

If you have trouble removing them, you may consider to saw or drill them. In order to anticipate such possibility in mind, you should prepare some new bolts, seals, and nuts.

In order to save you from extra work, we recommend you to purchase a catalytic converter that matches your car specification.

You may also buy a generic converter of course, but most of the time you’ll need to weld the generic part to fit it into your car.

If you buy a converter specific to your car, it will come pre-welded to the proper pipes, so that the bolts can be installed easily.

3. Before you can start to unbolt the catalytic converter, you should first use an O2 wrench to remove the oxygen sensor.

After doing this, you can now remove the pipe that connects the oxygen sensor to catalytic converter.

There are several exhaust systems that require you to remove more pipes in order to unbolt the converter from the muffler.

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4. Now it’s time for you to replace the old converter and install the new one. All you need to do is simply bolt the new catalytic converter to fit in place. It’s easy, isn’t it?

Attach the previously removed exhaust pipes and oxygen sensor. If you find any damaged, cracked, or rusty pipes, you should replace them while the exhaust system is still apart.

Okay now you’re done. However please put these things into your consideration:

Most catalytic converters have its own separate emissions warranty. This warranty usually lasts at minimum of 7 years and 160,000 miles.

If your car is a newer model, you may ask your dealer to replace the part free of charge even if the car itself is out of its regular warranty.

If you don’t own an O2 wrench or socket, you may consider to rent it. You can go to your local auto parts stores, many of them rent such tool.

In many states, Vintage or older cars are not required to use a catalytic converter, so if you want you can completely remove it.

A car running without a converter won’t damage anything except environment. So, from an ethical perspective such action is not recommended

According to emissions standards issued by the government, It’s strictly prohibited to buy or install used catalytic converters.

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Photo by oakridgelabnews You’ll need to have the basic knowledge of how a catalytic converter works before being able to understand the cause of its failure.

As part of your car’s exhaust system, the catalytic converter does its job by converting those dangerous compounds in the exhaust into somewhat harmless compounds.

In most passenger car, the catalytic converter has the shape that resembles a muffler.

It’s usually located between the muffler and the engine. It’s usually placed underneath the passenger seat on the underside of the car.

If you drive your car for a long trip, those who sit on the passenger seat may feel the warmth penetrates through the floor.

In United States, catalytic converters have been made standard for automobiles since the mid-1970s.

When leaded gasoline was still available many cars that used this type of gas had problems with their catalytic converters.

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The leaded gasoline contaminated the converters and destroyed their usefulness by clogging them. This was one factor that encourages the usage of unleaded gasoline.

A Peek Into a Catalytic Converter

Depends on the automobile type, usually after the exhaust gases of the engine pass through the catalytic converter, they will go further to the muffler or mufflers.

There are also some cars that use pre-converter that performs similar function.

Today’s catalytic converter usually functions well through the rest of car’s life. It rarely has a problem with clogging or plugging during its lifetime.

There’s a honeycomb set of passageways that’s located inside the catalytic converter. These passageways are usually made of small ceramic beads that are coated with catalysts.

Inside the converter, the pollutants are made less harmful through a chemical reaction that occurs.

The many passages are provided to allow for the maximum amount of surface area for the hot gases to flow through.

The Components of Catalysts:

• Oxidation Catalysts : Very small amounts of platinum (Pt) and palladium (Pd) metals. They are used for converting monoxide and hydrocarbons that’s generated by unburned gasoline into water and carbon dioxide.

• Reduction Catalysts : Very small amounts of Rhodium (Rh) and Palladoum (Pd) metals. The job of these catalysts is to remove nitrogen oxide by converting it into oxygen and nitrogen.

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It is an important task that these catalysts perform, since one of the big contributors to smog is nitrogen oxide.

In many states and localities, emission tests that check the actual emissions content are being held annually.

The purpose of exhaust emissions test is to find out if a converter is absent or there’s a malfunction.

Sometimes, a mechanic may remove the converter temporarily and replace it with a test pipe.

In some states and localities, removing a factory-installed catalytic converter is an illegal action.

So you may want to check with your local authorities to confirm such rule.

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There are two main reasons why a converter fails :

- The converter is poisoned

- The converter is clogged

There’s actually no way for us consumers or mechanic to take a peek into the converter in order to see an actual clog inside it.

Most of the time the converter must be removed and checked for the change in engine performance.

This is the common way to find out if the catalytic converter is plugged(malfunctioning).

When there is an indication that the converter is clogged, the mechanics will temporarily remove the 02 sensor to see if there are any changes in performance.

The mechanism of the converter relies on processing the proper mix of exhaust gases at certain temperature.

When the mixture or temperature of the exhaust gases change, the effectiveness and life of the converter will be reduced.

This condition is usually caused by additives contamination or malfunctions.

Over usage of leaded gasoline and certain fuel additives are the main cause of such problem.

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There are two other things that are responsible for a catalytic converter failure, they are:

- Unburned fuel that overheats the converter. This can be caused by fouled plugs.

- Damaged exhaust valves on the engine.

If you feel like you don’t go any faster even when you already push the gas pedal, then the converter is probably clogged.

You may also notice a significant drop in gas mileage when you drive using a clogged catalytic converter.

A partially clogged converter may affect the RPM of the car by limiting it to a fast idle.

If the converter is totally clogged it may cause the engine to quit after a few minutes.

The engine may quit due to increased exhaust back pressure.

Similar to the rest of the emissions system, the catalytic converter usually provides a warranty that exceeds the term of the warranty for all other warranties of a typical U.S. Vehicle.

One thing you should keep in mind : Never park your vehicle over piles of dry leaves or tall grass.

Why ?

Because it can cause your running catalytic converter to become extremely hot which eventually may generate fires.

If you want to keep your catalytic converter in good condition, you will need to maintain the ignition system regularly in order to keep the converter running in top performance.

A good ignition system may prevent the contamination of unburnt fuel inside the catalytic converter.

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Photo by makelessnoise Most original equipment converters are designed to operate until 100,000 miles or more. And in fact, many of them operate well until they reach the recommended miles for replacement.

But this assumes that the converters aren’t poisoned by lead, phosphorus and silicon.

When leaded gasoline was still widely sold, many cars’ converters that use such fuel suffered from premature demise.

The lead may coats the catalyst and make it unable to be rendered.

Silicon also shows similar effects as leaded gasoline. Silicon is widely used in antifreeze and several types of RTV sealer.

The common cause of silicon infiltration into converters is coolant leaks in the combustion chamber. The leaks enable the silicon to enter the exhaust and eventually contaminate the converter.

Phosphorus is generated from oil burning. The substance may produce some barriers inside the converter that will disturb the work of the converter.

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Unburned fuel in the exhaust may generate excessive heat that can cause the converters to fail.

Rich fuel mixture, ignition misfire (a bad plug wire or a fouled spark plug) or a burned exhaust valve that leaks compression are the main factors that contribute to such failure.

It would be like dumping gasoline on a bed of glowing embers if you have unburned fuel in the exhaust. Things inside the exhaust get really hot rapidly.

And when the temperature increases to a certain degree, it will melt the ceramic substrate.

The substrate is used to support the catalyst, so if it melts down it will cause a complete or partial barrier inside.

As the result of blockage, the backpressure increases and prevent the engine from exhaling. This condition will reduce the power which is generated by the engine.

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You may feel sluggish at higher speeds and the consumption of fuel will increase rapidly and extremely.

If the converter is fully blocked, the engine usually will stall after starting and it won’t restart again.

A dead converter is unable to be restored. You also don’t need to try to unclog or clean out a blocked converter because it just won’t work.

So when facing with a damaged converter, the only option is replace it with a new one.

Converters were used to be covered by a five year or 50,000 miles federal emissions warranty (In California, it’s 7 years or 70,000 miles). This warranty was intended for cars up to model year 1995.

In 1995 the warranty was made longer to 8 years or 80,000 miles.

The converters that are going to be used for replacement must be the same type as the original one.

It’s either two-way, three-way, or three-way plus oxygen. It should have EPA approval and you need to install it in the same location as the original one.

A dead or plugged converter will be solved by replacing it with a new converter. But the most important thing is you need to diagnose and correct the root cause of the problem.

Because if these underlying problems are still there, the new replacement converter will soon suffer the same fate as the old one.

Today’s Technician: Automotive Engine Performance Classroom Manual( 2 Volume Set)

So it’s best to check other items too when you have a dead converter problem. These items are air pump and related plumbing, feedback control system, and oxygen sensor.

If you have a sluggish O2 sensor, the fuel mixture is unable to switch back and forth between rich and lean quickly enough. If this is the case, the converter can’t work at its highest efficiency.

Perhaps this condition is not going to end up in a meltdown, but it can generate excessive pollution that will make your car fail an emission test.

If you keep using the sluggish oxygen sensor, it will most likely to fail someday. When this happens the fuel mixture will remain fixed and the engine will run too rich in fuel. As the result, your car will waste lots of fuel as well as producing high level of emission.

Many car manufacturers recommend us to check oxygen sensors at specific mileage intervals. This should be done in order to prevent car owners from problems that are related to oxygen sensor.

Today’s Technician: Advanced Engine Performance CM/SM

Most imported cars have a reminder light that may illuminate every time the car reaches the 30,000 miles or so interval.

The light is to remind the vehicle owner to check his oxygen sensor and replace it when necessary.

Bosch, one of the leading supplier of oxygen sensors suggests vehicle owners to replace their oxygen sensors at roughly the same interval as the spark plugs for preventative maintenance.

You should replace the oxygen sensors of 1976 to early 1990 cars that use unheated 1 or 2 wire oxygen sensors every 30,000 to 50,000 miles.

For heated 3 and 4 wire O2 sensors on mid 1980s to mid 1990s vehicles, you should replace them every 60,000 miles.

If you have a 1996 vehicle and it’s equipped with newer OBD II, the recommended interval for replacing the oxygen sensor is 100,000 miles.

http://www.metacafe.com/watch/yt-TY2RU2UHf8M/

Watch this Nice Video and learn more about Emission System

Photo by Podknox Emission controls were first introduced in the late 1960s. Their primary purpose was to solve a particular emission need.

Back at that time, these devices were treated as “add-on” components only.

Blowby emissions used to be the main pollutant of automotive. In 1968, the positive crankcase ventilation (PCV) became standard.

By recycling the crankcase vapors, the device successfully eliminated blowby emissions.

Another factor that contributed to air pollution was fuel vapors. In 1971 evaporative emission controls were added. The sealed fuel systems and charcoal canisters successfully eliminated the fuel vapors.

In 1973 exhaust gas recirculation (EGR) was added. This reduced hazardous oxides of nitrogen emissions that are produced by automobiles.

However, in 1975 the government required auto makers to install the most significant add-on on all new manufactured vehicles, those add-on were catalytic converters.

The catalytic converter was a big breakthrough in emission control technology. What it basically did was reducing Carbon Monoxide (CO) and unburned Hydrocarbons (HC).

Carbon Monoxide is a very hazardous pollutant since it can be deadly to humans even when they are exposed only to small concentrations.

While Hydrocarbons (HC) is the primary factor that forms urban smog.

The catalytic converter has the ability to reduce 90% of the levels of such pollutants.

The early converters were called “two-way” converter because they reduce the two dangerous pollutants (CO and HC).

They work like an afterburner in the exhaust by reburning the pollutants.

In order to burn those pollutants effectively, an air pump or an aspirator system were used to supply extra oxygen.

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From 1975 to 1981, the two-way converters were installed on every new car. Three-way converters were introduced as the successor of two-way converters.

These converters had the ability to reduce NOX concentrations in the exhaust.

But in order to do it the converters need an addition of computerized system to control the fuel concentration.

The three-way converters worked differently from the two-way ones.

The two-way ones may operate well in a lean fuel mixture, but the catalyst inside the three-way ones require a rich fuel mixture in order to reduce NOX.

The rich fuel condition produces an additional problem because it raises CO levels in the exhaust.

In order to reduce these three pollutants (CO, HC, and NOX), a three-way converter needs a constantly changing fuel mixture that goes back and forth from rich to lean.

Today’s Technician: Automotive Fuels and Emissions. Classroom and Shop Manual Set (Bk.1)

To maintain the lean and rich flip flops, the engine requires an electronic fuel injection and an oxygen sensor. The electronic injection regulates the amount of fuel that’s injected.

While the oxygen sensor is required to read the fuel mixture condition in the exhaust and send it to the computer to process the information.

Three-way converters also need extra oxygen that’s supplied by an aspirator system or an air pump.

There are “three-way plus oxygen” converters that are designed to make sure air is routed right to the converter to maintain a more efficient operation.

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A1 Cardone 32291 Remanufactured Smog Pump

1995 Honda CBR 600 F3 Emissions Control Valve And Hoses

2002 Suzuki GSXR 750 Gsx-r 750 Emissions Control Valve And Hoses

1990 Kawasaki ZX6 ZX 6 D Ninja Emissions Control Valve And Hoses

http://www.metacafe.com/watch/1842494/

No matter what kind of car you drive, You should watch Lauren Fix, the Car Coach, she will show you how to gain a better gas mileage. She shared practical things that almost everyone can easily do to save more dollars on gas.

How many of us who face difficulties when trying to find out what causes the starter problems on Camrys?

Fear not, let’s learn how to perform several easy tests to find out the cause of the problem.

They are simple tests, you will need a test light. You may also prepare a multimeter in case we need it.

Many times, starter system problems are caused by loose or damaged connection, it’s also possible they are caused by worn out component that has stopped operating.

Starter Doesn’t Operate at All

If you experience that the starter doesn’t operate at all, you may perform a simple test which can help you trace the problem.

Now, try turn on the headlights and ask someone to turn the ignition key to “Start”. Observe the lights, if they remain bright, you may want to check for a bad or open component in the circuit of starter.

Now follow the path along your starter circuit, use a test light to help you do this. Begin the checking from the battery, see if there’s a loose connection or corosion, dirt or grease.

As you test each connection at the ignition switch, neutral start switch, and solenoid, ask a friend to turn the ignition to key to “Start”.

When your test light bulb does not come on, it means the voltage stops on that connection. If this happens, that is the troublemaker.

If during the first test the headlights dim, you should the check the battery for voltage. Make certain that all of the connections in the starter circuit are in tight and clean condition. You may take the starter to your local auto parts store or auto shop for further test.

Starter Makes Noise

The first step is check your battery whether it has the correct voltage or not. Check every connection,make sure they are clean and tight.

When necessary, you may raise the front of the Camry. Support it using jack stands. Use a ratchet or wrench and socket to make sure the mounting bolts of the starter are tight.

You may want to make sure you installed the correct starter if you have just replaced it.
If you installed the wrong one, the flywheel ring gear and pinion gear on the starter won’t mesh properly.

At each component in the starter circuit you should do a voltage drop test at the connections. Use your multimeter to do this.

Now probe the terminal and the fitting at every component connection. If everything is normal the voltage should not exceed 0.5 volt.

If you deal with an old motor starter, those defective or worn internal components are most likely fail to operate the pinion gear properly.

When necessary, detach the starter and bring it to your local auto parts store or auto shop for further tests.

Starter Operates Slowly

Similar to previous tests, you may want to check for proper voltage at the battery and make sure all starter circuit’s connections are in clean and tight condition.

Perform a voltage drop test at every connection as explained in the previous “Starter Makes Noise” section.

Raise the front of your car and check to make sure that all the connections are secured and the starter is tightly mounted.

If necessary, remove your starter and bring it to the nearest auto parts store or auto shop for further examination.

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Watch the video on How to Change Starter on Nissan Sentra

http://www.metacafe.com/watch/yt-31xZMpesBXU/

Photo by follettmotors_com These days, most cars have engine control systems that respond to inputs from various sensors. These systems work to adjust and regulate emissions, engine performance, and other major functions.

These sensors are required to give precise information to prevent unnecessary fuel consumption, emission failures, and driveability problems.

Oxygen sensor is one of the key sensors that gives important signal to computer system in the engine.

Oxygen sensor is usually called O2 sensor. It was first introduced in 1976 on 240 Volvo vehicle. In 1980, California issued its emission rules that required lower emissions. During this time more and more cars were equipped with O2 sensors.

And in 1996 the government issued OBD-II regulations. The auto manufacturers responded it by producing cars with multiple oxygen sensors, some had as many as four.

In order to monitor unburned oxygen as the exhaust exits the engine, an O2 sensor is attached in the exhaust manifold. This monitoring is done to adjust fuel mixture.

When the sensor senses low oxygen it means the fuel mixture burns rich, the system will respond by injecting less fuel.

When the O2 sensor signals high oxygen,it means the fuel mixture burns lean, the system will respond by injecting more fuel.

There are several other factors that may affect the fuel mixture condition (lean or rich). They are engine coolant temperature, throttle position, air flow, engine load, barometric pressure, and air temperature.
All these factors are monitored by sensors.

But the most essential information is the signals that are retrieved from O2 sensor.

So if there are problems with the oxygen sensor, this may generate significant impacts on the engine and its performance.

The process of computer system regulating fuel mixture based on inputs from oxygen sensor is called “feedback control loop”.

Photo by lumachrome This loop works as follow:

The computer system reads the signal from oxygen sensor and respond by adjusting the fuel mixture. This action will change the fuel / oxygen ratio, because the condition changes the O2 sensor reading changes. The computer system will then respond to this change. The system works on and on like this, flip flop back and forth from lean to rich.

This loop enables catalytic converter to perform at highest efficiency while maintaining the proper balance of overall fuel mixture. The whole mechanism will produce minimum emission.

Well does this system look complicated to you ? Yes It is complicated, but fear not what you need is just understand the big picture.

When a cold engine is first started, the oxygen sensor usually sends no signal,if this is the case the computer system will adjust to rich fuel mixture. The same condition also happens when the O2 sensor fails. This situation is referred to as “open loop” operation.

If the engine is unable to enter closed loop (ideal condition, flip flop from lean to rich), the engine will run in over rich condition that will waste much fuel and increase emissions.

This may happen when oxygen sensor fails to send signal once it reaches operating temperature or the O2 sensor’s signal is lost.

Another possibility is a bad coolant sensor. In order for the computer to decide whether or not to enter closed loop, it will also check the engine coolant temperature.