Auto Service World
Feature   March 1, 2004   by John G. Smith

Long Life, But Too Often Forgotten?

Spark plugs and O2 sensors continue to improve, but there is still a replacement market

You would think that those who sell spark plugs would pine away for days when V8s ruled highways and nickel-tipped plugs were swapped after 30,000 km of service. After all, a four-cylinder engine needs fewer spark-producing components, and double-platinum and iridium designs last well past 100,000 km.

“That, from our perspective, is in the best interest of the customer,” says ACDelco senior product manager Nancy Lee, referring to the ever-extending life spans.

Consider recent improvements in premium plug designs. The melting point of iridium is 700 Celsius higher than platinum, Lee notes of the latest precious metal to be embraced, adding to the life of the components. And their smaller tips — now measured in terms of the points of two pins — put a lesser drain on electrical systems.

Regardless, even the newest spark plugs will eventually need to be replaced and installers would be well served to pay more attention to the parts.

Some technicians will use whatever a jobber sends through the door, while others will simply use whatever model is threaded in place by an OEM, regardless of whether a superior plug is available, admits NGK product manager Jeff Desveaux. Sometimes, they even base their decisions on long-outdated information. Champions were once considered the standard spec’s for Fords, while current models can include NGK plugs, he says. (And where NGK might be assumed to offer the spark for an import, it might carry another label.)

Updates haven’t been limited to longevity alone. Honeywell Consumer Products’ Autolite unit recently unveiled a 10-mm plug for the 2004 Ford F150 Triton, claiming to match the dielectric properties and durability of 14-mm designs. And the company expects smaller sizes to become a bigger issue because of constricting engine spaces.

“It’s truly groundbreaking,” Autolite vice-president Eric Rozier said when releasing the plug this January. “This new spark plug provided engine designers with more space for an additional intake valve and unobstructed intake ports, enhancing power and creating more efficient air flow without increasing the engine’s size.”

Whether the smaller size will be the trend of the future is a matter of debate, Desveaux says, suggesting that plenty of space still exists. In fact, he thinks a bigger trend will involve refined installation procedures.

Plugs in a Honda Insight now need to be indexed, Desveaux notes. And he expects other manufacturers to adopt the procedure once limited to racetracks. “That can be the next big thing.”

Indexing involves aligning a spark plug’s electrode to face its corresponding intake valve, aiming the spark directly into the incoming charge of air and fuel, and reportedly delivering a small increase in power. (It’s accomplished by putting a washer under the shoulder area of the plug, to ensure the electrode’s alignment once everything is torqued in place.)

Another tune-up-related component to enjoy an extended life is the oxygen sensor, although other forces have made this part a more common replacement item.

The sensors that monitor hydrocarbons and oxygen have since the mid’-70s played an important role in ensuring optimum stoichiometric air-to-fuel ratios of 14.7:1. But it may have taken the introduction of mandated emission tests to convince consumers that the parts should be inspected before the flash of a “check engine” light.

Bosch, the company that introduced the sensors in 1976, reported in 1998 that 99.7 per cent of consumers didn’t even know that they had oxygen sensors on their cars. When B.C. began its mandated AirCare emissions tests, the related replacement components were most likely a catalytic converter, gas cap or spark plugs. Oxygen sensors didn’t even make the Top 5.

Since 2000, they’ve become the top replacement component surrounding emission-related repairs. After all, the California Air Resources Board (CARB) concluded in 1998 that, “failed/poisoned oxygen sensors were the leading cause of excess, harmful exhaust emissions.”

And the number of replacements is bound to increase, says NGK product manager Chris Harrison, referring to how the current generation of OBD-II systems was first introduced in 1996. “These vehicles are now coming into the sweet spot of incidents of repair.”

While different generations of the sensors perform the same function, they have evolved. Early two-wire designs were mounted in the engine manifold and didn’t include integrated heaters. Even the planar sensors first introduced in the 2.0-litre 1998 Volkswagen Beetle have improved. Bosch now has a design with the platinum electrodes, conductive layer of ceramic and heater laminated together on a single, layered strip, reaching operating temperatures of 625 to 650 Fahrenheit in a matter of 10 seconds — ensuring emissions are monitored soon after the turn of a key.

“Nearly half (of the cars on the road) were built before OBD II regulations came into effect, and are equipped with one or two unheated thimble-type O2 sensors or heated thimble-type O2 sensors, mounted upstream from the catalytic converter. Another half … are OBD II vehicles, and are equipped with from two to four heated thimble-type or heated planar O2 sensors. This includes sensors upstream (before) the catalytic converter and sensors downstream (after) the converter,” notes Norihisa Akamatsu, group product manager, engine management products for Robert Bosch Corp.

If there is excessive air in the exhaust, the sensor reads a voltage near zero. A rich, fuel-filled exhaust generates a reading of .8 or .9 volts.

An optimum reading is around .45 volts, although the sensors also watch cross counts — the voltage that fluctuates back and forth across the magic threshold — to ensure that they’re providing proper readings and are not simply blocked by carbon.

Heated wide-band sensors, largely used on imports, include a pumping cell that can produce a signal directly proportional to the air/fuel ratio, rather than simply switching back and forth between a rich or lean reading. Harrison expects such designs to emerge in North American models in just a few years.

But even sensors designed to last 120,000 km may require early replacements. Sensors, for example, can foul because of cracks in the cylinder head, or silica poisoning that comes from antifreeze-related contamination. It’s why NGK recommends that installers check long-life sensors at 60,000 or 80,000 km. And installers should beware of the anti-seize material used on threads, because the wrong choice can poison the sensor, leading to problems such as a damaged catalytic converter.

“Because of the aging installer population, many were in the business before sensors even came in. They don’t know enough about the components and OBD II,” Harrison adds of how well the sensors are understood at the shop level.

Perhaps it’s Greek to them. (Appropriate, really, given that the first sensors were known as Lambda’s — a letter of the Greek alphabet.)

As its solution, NGK now has a full-time employee who does nothing but travel the country to hold clinics with installers. The company is also looking to developing a related certification and rewards program.

Then again, the revenue from additional replacements can be a reward of its own.

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