Special Report Clearing the Air About Smog Tests

February 1, 2011 | By Don Kenyon

Many Are Faced With Regular Checks for Their Newer Cars. So, We Asked a Smog Tech to Help Us Prep.

Editor’s note: Many vintage cars are exempt from regular state smog tests, but as more people are restoring and maintaining ’80s and ’90s vehicles, along with having an even newer daily driver in the garage, multiple smog tests have become a part of everyday life. To help us all better understand this subject, we turned to DonKenyon,who describes himself as “a severely addicted old car buff who just happens to be an ASE Master Tech and a California Enhanced Smog Test Technician.” Don also owns a smog test and repair station in central California.

ANYONE CAN DO my job, just ask my customers...I stand at the TAS(Test Analyzer System) computer terminal and punch in the VIN (vehicle identification number) orI sit in a relaxed position in your vehicle while the emissions test is performed—anyone can do that!

I’m sure I often look half-asleep and completely disconnected from my task, all the while someone’s beautiful car is being sent to the slaughter of the dreaded “gross polluter” designation.

Everyone seems so sure that their beloved ride is just one step from the recycling center...they’re scared...or mad I understand that emissions testing is the red-headed stepchild of auto repair. Everyone in the auto repair industry gets more respect than I do—the body man, the painter, the engine builder—even the quickie-lube guy.I often get inquiries as to whether I can actually repair a car— despite being anASEMasterTechnician with over 30 years of general automotive repair and nearly 20 years of emissions(smog) testing and repair. Oh, and 25-30k smog tests under my belt.

Know What You’re Up Against

So, why do so many people fear or hate or misunderstand what I do?

This article is intended to help convince you to stop being terrified of the smog inspection process by being completely informed of what’s actually occurring. You, as a rare and cool vehicle owner are much more in tune with what’s happening with your engine and its related parts than a hundred smog guys. All you need is a little educating as to the cause and effect of the five (four in some places) measured gases exiting your gleaming (on the outside) tailpipe. And a couple of other important things...

Antique, muscle and special interest vehicle owners want to know everything they can…you folks live for expanded knowledge on your vehicles.

So now the rest of the smog story can be revealed—why did my beautiful beloved fail the smog test? What can I do to get it to pass? How do I prevent a future failed test?

Smog ’Round the World

At this writing the folksin Moscow are coping with heavy smog. Droughts have caused widespread forest fires and the smoke from these fires has settled in their city.Mexico City has suffered from terrible smog problems for years. (Substantially due to the decades-long and just recently ceased production and sale of the air-cooled Volkswagen Beetles.) Indonesia suffers from smog due to rapidly developing industry in China, South Korea and other Asian countries.

Closer to home, metropolitan areas in more than one state are experiencing smoggy days, and this reality has prompted different versions of the good ol’ emissions test.

Brought to You By…

Ever wonder where smog test programs originate? Compounding what you may already think of us, California (especially Southern California) has led the United States in the development of these tests. A lot of what’s been learned about what works and what doesn’t work has come from California. It’s important to know that smog tests are seemingly ever evolving.

Anyway, many states’ emissions test programs are based on the FTP (Federal Test Procedure); California’s is.

Our ASM 25/50 is a tiny piece of the FTP’s I/M 240. ASM stands for Acceleration Simulation Mode and 25/50 stand respectively for the amount of load placed on the tested vehicle via a dynamometer, 25 and 50%. I/M stands for Inspection and Maintenance, and 240 is the number of seconds the tested vehicle must run the driving part of the test (via simulation on a dynamometer).

OBD-II and You

If your state has an emissions test at all—some states like Hawaii and Montana don’t have one, it may only be an “OBD-II” test with or without some sort of basic safety test like there is in Pennsylvania.

Anyway, “OBD-II” means On Board Diagnostics-II. (OBD-I was whatever computer system your favorite brand of car had before about 1996. OBD-I on General Motors, for example, was quite advanced. On certain other cars—especially the low-priced Japanese ones, OBD-I might only consist of an “auto code read” function and no live data.)

If your 1996 or newer vehicle hasto be tested, then, the smog technician will have to find your often hidden OBD-II connector and plug in his computer in order to get a readout.In California we’re looking for much more than just DTCs (Diagnostic Trouble Codes). The sophistication of 1996 and newer OBD-II systems mean that your vehicle’s sensors and especially its emissions devices are monitored by the PCM (Powertrain Control Module). These monitors are also called self-tests and these mini-computer programs within a computer program have revolutionized smog check, and much more profoundly, auto repair.

In the past when a technician diagnosed and repaired your vehicle’s emission or engine control systems, you often had to take his word for it. These days, I can claim I fixed your car and charge for the repair but until your vehicle’s computer has dynamically tested that device and not set some sort of related code, the darn thing isn’t fixed. OBD-I had about six or 10 codes you saw all the time,OBD-II has many times that! OBD II is constantly checking and rechecking many more devices in many different ways. Computers have no sense of humor or mercy.

No longer can automotive technicians shun classes, seminars and other training related to their field. I guarantee that the old “shoot from the hip” way of computerized engine repair diagnosis will no longer fly. It may fix a few or even a little more than 50%. But that still leaves a lot of angry customers coming back to give you a piece of their minds. OBD-II always has the final say!

Time for a Chemistry Lesson

The “up” side of all this smog business, the PCV (positive crankcase ventilation) valve.
The “up” side of all this smog business, the PCV (positive crankcase ventilation) valve. It lengthens engine life, keeps oil cleaner and helps burn off emissions that would otherwise enter our atmosphere.

The engine in your rare beautiful beloved is performing a chemistry project on every stroke of its mighty pistons. It’ssucking a varying mix of atmospheric gaseous material made up mostly of Nitrogen Gas with a little bit of Oxygen Gas and even smaller amounts of Argon Gas, Carbon Dioxide (the greenhouse gas) and even water vapor either dissolved in the aforementioned gases or by itself. This gaseousstuffisthen mixed with something that used to be called gasoline. If your beautiful beloved runs on propane or alcohol or natural gas, don’t put your nose in the air asif you’re “Mr. Green.” These alternate fuels can pollute every bit as much as gasoline.

But What Does That Mean?

An emissions test failure should be followed by a technical readout of some sort. After all, what are you paying for? In California this is called a VIR (Vehicle Inspection Report). The five usually discussed gases exiting your tailpipe are as follows: HC, CO, NOx, O2 and CO2. The O2 and CO2 are called “diagnostic” gases as they can help you diagnose a failed test. The first three are the actual pollutants, although CO2 seems to play on either team, you know?

Anything that can make an engine run poorly, including old gas, bad gas, a stuck-open thermostat, fouled plug, bad wire, blown head gasket, burned valve, whacked sensor, and on and on will contribute to higher than expected HCs or Hydrocarbons. Hydrocarbons are only unburned raw fuel. That is, somehow they’ve managed to be found, drilled, removed, refined and then pumped into your vehicle by your own hands…only to somehow pass out the tailpipe in their original state. They’re measured in PPM or parts per million. A 1990s Chevy truck, for example, might be allowed about 120 PPM HCs max on a dyno smog test. By the way, that’s a tall order for an older TBI (Throttle Body Injection) Chevy truck...

If that lucky HC (Hydrocarbon)should be only partially burned before exiting the tailpipe then CO or carbon monoxide will result. CO, of course, is a deadly poisonous gas that can kill people. However, old age will get you a lot sooner than if you try to poison yourself with CO from a tailpipe of recent vintage. The above 1990s Chevy Truck, for example, might be only .10% CO as actually measured. That is, one tenth of a percent. CO is measured as a percent. For anything from the last 20-plus years that is fuel injected and with a catalytic converter, 1% COisich. The higher the CO in percentage the richer the mixture is.

A perfect or STOICHIOMETRIC ratio for gasoline is 14.7 parts air to 1 part gasoline. With a rich mixture—higher CO, the ratio will be more like 10 to 1. A too-lean mixture (low CO) will be more like 17 to 1. Anything that affects fuel mixture from sensors to choke setting to float level, fuel in the engine oil or a malfunctioning evaporative emissions system can cause a CO failure. I’ve seen failCO readings of over 10%.That makes your eyes burn!

Now, About NOx

This leaves us with NOx (oxides of nitrogen). The above processes affect NOx output (also measured in PPM) but are usually considered to be caused by a completely different thing. For example, 99% of the time a tune-up won’t lower NOx and may, in fact, raise it!

As I said earlier, our atmosphere is comprised mostly of Nitrogen Gas,(like 80%). Nitrogen is listed on the Periodic Table of the Elements as an inert gas. Inert means it doesn’t readily combine with any other atoms. However, under the heat and pressure of the combustion process, Nitrogen Gas combines in varying ways with O2 gas, creating NOx.

The X of NOx relates to the number of O2 atoms in each NOx molecule. Higher than expected NOx in your vehicle’s exhaust can be caused by over-advanced timing, lean mixtures or malfunctioning emissions devices. This may sound like heresy, but high NOx (and/or high CO2) can be considered the natural result of good combustion.

A typical GM air injection pump. GM-style pumps were used on Volvo, Mercedes-Benz and other car brands through the years and, of course, on Pontiac, Olds, Buick, Cadillac, Chevy, etc.
A typical GM air injection pump. GM-style pumps were used on Volvo, Mercedes-Benz and other car brands through the years and, of course, on Pontiac, Olds, Buick, Cadillac, Chevy, etc. Air injection is a very good way to lower hydrocarbons and carbon monoxide in automotive exhausts.

Oxygen and Carbon Dioxide

Nothing I know disheartens a true carlover more than a failed smog test. Alongside the three pollutants listed on your failed smog test are two diagnostic gases—CO2 (carbon dioxide) and O2 (oxygen). Please remember that air is not pure O2, it’s only about 19% or so and varies with the seasons of the year and other things.

Generally speaking, high CO2 readings(sometimes up to 14-17%) are good indicators that the engine and/or catalytic converter are working efficiently. In other words the better the burn the higher the percentage.

O2 readings in the exhaust are rarely above 1% on a modern car. Older cars with mondo air-injection systems might show 3% or more. Never do deep diagnosis with 5-gas readings without temporarily disabling and then re-enabling the air injection. It’s a long story for a future article (I hope). Just trust me for now…

A Textbook Definition

So, here’s what makes up the official description of smog as we know it: unburned hydrocarbons (HC) plus oxides of nitrogen (NOx) in the presence of sunlight produces smog. Choking, lung-tightening, vista-destroying smog. Basically ozone (O3).

There are lots of other pollutants floating around us caused by diesel engines, farming, industry, forest fires, drought and so on. These can cause their own types of smog. Right now, we’re only concerned by what our beloved automobiles produce.

One More Thing About the Process…

Anytime you burn (oxidize) something, in this case gasoline, you get yet another byproduct of combustion. This other substance is water—H2O. You wouldn’t think that water would be the product of fire or an explosion but there it is. This is one reason your vehicle spews water from its tailpipe on cool days.

I Know They’re Out In the Garage, Somewhere

Somewhere in a landfill is a huge assortment of early emissions devices ripped from engines by auto enthusiasts seeking ultimate power, fuel mileage and drivability from their rare beloved beauties.

Even now just mentioning these devices in some circles will result in rolled eyes and groans. Things like PCV (Positive Crankcase Ventilation), Air Injection, EGR (Exhaust Gas Recirculation) and the exalted leader—the Catalytic converter. Throw in ignition advance controls (like the NOx kit sold in California for 1966 to ’70 vehicles) and you can see again why I get no respect. Add to this mess the fact that many vehicle owners found their 4-wheeled best friend ran poorly after being “adjusted to pass” the smog test.

At this point—here’s something else to consider: HCs and CO burn like logs in a fire. This combustion process is exothermic. In other words, their reaction with oxygen causes heat. Add extra air to the process (air injection—either pump or pulse) and you get more combustion and more heat. This “afterburner” effect does a mighty good job of cleaning up HCs and CO. HCs and CO are oxidized (burned), NOx is reduced. In this case “reduced” refers to an actual chemical expression that means the molecules of NOx are torn apart. Please understand here that the processes that create and reduce HCs and CO are different (although related) from what creates and reduces NOx. Reducing NOx is an endothermic reaction. In other words it takes heat to perform this reaction.

You can see then that the emissions devices hanging off your prized possession are usually either for HC and CO oxidation—air injection for example. Or only for NOx reduction—for example an EGGER (EGR) the much-hated mushroom. One big exception is the Catalytic Convertor. Some 99%+ of the vehicles I see have Three-Way Converters (TWC). In other words, they work on all three HC, CO AND NOx.)

A Quick Rundown On Emissions Devices

Air Injection: Found on just about every make of car at one time or another starting in the mid-1960s, air-injection has to be one of the most benign systems ever. Yes, it complicates things with its extra plumbing and drive-belt and pump, but the benefits are immense.

As I said before, adding extra air into the hot exhaust does wonders for CO and HC cleanup. In fact, many Toyotas of the ’60s through 1980s rely on air injection to do the heavy lifting of HC and CO extraction.

When so equipped, pulse air injection relies on the pressure-vacuum wave of the exhaust pulse to suck outside air in a little at a time, thereby lowering HC and CO.

The PCV: Nothing is more benign under your hood than the PCV system. Rather than allowing crankcase gases to enter the atmosphere, the PCV system sucks them into the intake manifold and they’re consumed. A side benefit is cleaner oil and longer engine life.

Egger (EGR), the much-hated and misunderstood mushroom: Where do I begin? Was there ever an automotive emissions device more suspected of causing harm and/or drivability problems with a car? The EGR system’s function defies logic: bypass a little exhaust back into the intake where it will cool off the combustion chambers and lower NOx…and make you car run poorly! Except it doesn’t run poorly when the EGR flow is correctly modulated. As you probably know, early EGR systems often had terrible modulation. Newer cars actually require EGR flow in order for the vehicle to run properly. It seems that the “inert” pre-burned exhaust gases displace fuel/air mixture under warmed-up part throttle conditions and will raise fuel mileage, keep the engine from overheating and/or pinging. Doesn’t sound like the EGR I know..

TheCat: Everything from low power to no-starts are often blamed on the catalytic converter, and under certain operating conditions and the vehicle’s year of manufacture—these suspicions are definite possibilities. On older vehicles without fuel control (no O2 sensor connected to a computer connected to some kind of mixture solenoid or fuel injector), the cat converter’s life can be short and hellish. If it is stuffed with enough pollutants (HC and CO), the cat just gets hotter and hotter until it plugs or sends pieces into the muffler or both. In extreme cases the cat’s expensive interior materials will vaporize and produce a colored smoke unlike any you’ve ever seen from a car.

If you’ve ever smelled rotten eggs while following a vehicle up a grade then you’ve experienced a hot cats mell.

Misfires are the cat converter’s number one nemesis. This is why 1996 and newer vehicles flash the “service engine soon” light during an engine misfire event.

Questions I Hear All the Time

After about 20 years of emissions testing and repair you begin to hear the same questions from customers on a very regular basis.

For example: “I run cheap gas all the time—should I be running a brand name?”Another is: “Does that Guaranteed To Pass Smog Stuff they sell at the DIY auto store work?” Or one of my favorites: “Does all this smog stuff do any good?”

Well, I don’t have to tell auto enthusiasts to run good gas in your rare beloved beauties; I know you wouldn’t run that no-name stuff. And no, the Guaranteed To Pass Stuff doesn’t work—its only active ingredient is fear.And finally,well, this gets personal.

A typical GM-style EGR (exhaust gas recirculation) valve.
A typical GM-style EGR (exhaust gas recirculation) valve. GM valves were originally made by GM’s Rochester Division. The best replacement for GM EGR valves are either NOS Rochester valves or a superseded Delco EGR valve, when available. Never discard a GM-style EGR valve just because it won’t hold vacuum. Many GM EGRs need to see exhaust backpressure internally in order to start holding vacuum.

If your tastes in “older” vehicles run to cars such as this 1983 Nissan 300ZX,
If your tastes in “older” vehicles run to cars such as this 1983 Nissan 300ZX, you’ll be taking your collector vehicles in for smog tests along with your newer daily drivers. And in case any non- Nissan fans are wondering, “Fairlady,” as seen on the front bumper, is what the car was called in Japan (NISSAN MOTOR CO. PHOTO).

Mountains? What Mountains? Hey, There They Are…

I grew up in the Greater Los Angeles area during the ’60s and ’70s. My family lived just a few miles from the foothills of the San Gabriel Mountains. Yet every summer those beautiful hills were nowhere to be found. This was at a time when many of the valley communities were just beginning to change from agricultural-based(mostly citrus)to housing developments as far as the eye could see. Far fewer people lived there at that time.

Now when I visit where I grew up I find that more often than not you can see the hills and the San Gabriels. This despite the fact that the population has exploded. Yes, this smog stuff is doing some good!

Now, just in case you think I’m a government spy sent in to demolish the old car hobby, let’s be clear: I love old cars! I own at least a dozen of them from a ’65 XKE to a ’33 IHC rat rod to a ’41 Dodge Panel 4wd conversion.

At this juncture I’ll entertain the possibility of answering an emissions related question or two from passionate automotive enthusiasts such as you. As Larry Lyles always says: “Send them along.”