If the scheduled maintenance guides in most vehicle owners manuals were to be believed verbatim, the 100,000-mile tune-up has doomed aftermarket ignition parts to marketing oblivion. Just as the smell of gasoline spelled doom for the buggy whip industry of 100 years ago, any whiff of the words "maintenance-free" seems to spell a similar doom to various segments of aftermarket parts. After all, the numerical evidence seems to be there: the market generated by the annual, 12,000-mile tune-up interval of two decades ago has eroded to the more meager 100,000-mile interval of today. Mathematically speaking, current sales should only be one-eighth of what it was 20 years ago.
But, has the ignition parts market really declined, or are we simply missing sales opportunities by measuring todays ignition market with the yardsticks of the past? The case for increased opportunities should be expressed in terms of more vehicle miles driven than ever before and of more auto manufacturers adding more cylinders per vehicle than ever before. Last, on a per-ticket basis, the potential for ignition parts sales is soaring. A spark plug replacement on some vehicles can cost the customer between $100 and $200 on many vehicle applications. On vehicles with limited accessibility, prices can soar well over $300 for, yes, "just a spark plug replacement."
THE OLD MARKET
To paraphrase a bit, old cars never die; they just gradually rust away. So, its important to remember that many pre-1995 vehicles equipped with parts-consuming mechanical devices like distributors are going to need more service than ever before.
Technically speaking, most early distributor ignitions rarely exceeded 25,000 volts at the spark plug, so they rarely failed due to electrical stress. Unfortunately, as voltage demands routinely began to exceed 30,000 volts in the early 1970s, worn spark plug gaps and open-circuit spark plug wires would stress the distributor and cause arcing in distributor caps and burn-throughs in distributor rotors. Worse still, an extremely active form of oxygen called ozone would hasten deterioration of the distributors metal and electrical parts. Obviously, as long as distributors are around, the market will always exist for caps, rotors, ignition modules, magnetic and hall-effect pickups, and perhaps a remanufacturing of the whole distributor itself.
What are the high-demand replacement parts in distributor ignitions? Most qualified technicians consider replacing the distributor cap, rotor and spark plug wires as a routine maintenance procedure. Next, an ignition module failure is perhaps the most common catastrophic, no-start failure in a distributor ignition. Last, wear in the distributor shaft bushing (as in many Honda applications) and the mechanical advance mechanisms (as in many General Motors HEI ignitions) comprise the major driveability failures in distributors. Considering that increasing ignition maintenance needs may offset declining populations of distributor-equipped vehicles, the distributor market may be slowing but is far from gone.
THE NEW MARKET
Advancing technology, of course, has made it possible to eliminate the distributor altogether by using computerized electronics to control spark timing and cylinder-to-cylinder spark distribution. Distributorless-ignition system (DIS) coils, for example, are now designed to fire two cylinders, one of which is on the compression stroke while the other is on the exhaust or "waste" stroke.
In order to time the spark, distributorless-ignition systems use a crankshaft position sensor (CKP) to signal the engines powertrain control module (PCM) or computer when the #1 cylinder reaches top dead center. When the PCM receives the CKP signal, it triggers the ignition module, which in turn activates the ignition coil and creates the necessary spark to ignite the air and fuel mixture in the engines #1 cylinder.
Of all the DIS-ignition components, the CKP is the most failure-prone and the most likely to cause a cranking, no-start, no-spark complaint. Since CKPs are mounted close to the crankshaft or flywheel, they are usually exposed to water, oil and vibration, neither of which will contribute to the longevity of the part. As for multi-coil ignition systems, the more coils, the higher the probability of developing a driveability complaint.
THE CLEAN BURN
To better understand modern ignition systems, its important to remember that electronic fuel injection has produced the fuel-metering characteristics needed to provide a clean-burning air/fuel mixture. Electronically controlled exhaust gas recirculation (EGR) valves have also reduced cylinder combustion temperatures, which, in turn, have reduced wear and tear on spark plugs. Last, engine oil consumption has also been drastically reduced to prevent carbon-based contaminants from fouling spark plugs.
In response to these and other developments, spark plugs, distributor caps, rotors and spark plug wires have begun lasting well over 100,000 miles. As might be expected, this extended replacement interval has brought on its own series of unintended consequences in the ignition parts market.
Conventional spark plugs designed for cast-iron cylinder heads are usually made with threads cut into steel shells. While roughly cut threads can be very forgiving on cast iron, they quickly seize to a soft-metal aluminum cylinder head. In direct contrast, modern, long-life, spark plugs are made with the threads that are smoothly rolled into the steel shell and coated with various metal alloys that wont stick to aluminum.
To prevent electrode wear, the electrodes on long-life spark plugs are also coated with precious metals like gold and platinum. Because a DIS-ignition coil fires with positive polarity on one spark plug and negative polarity on the other, an OEM spark plug may be coated on either the positive or negative electrode in order to cut manufacturing costs. In the world of replacement spark plugs, both electrodes are coated with precious metal so that the technician wont confuse the positive and negative-firing cylinders, thus the term "double-platinum spark plug." Consequently, its easy to see the price and profit difference between the old "$1.98" steel-shell, cut-thread spark plug of 1972 and the $11.98 plated shell, rolled-thread and precious-metal spark plug of 2003. Fewer spark plug sales, yes, but were selling at much higher prices and wider profit margins.
BOOTS N WIRES
One of the last issues to consider in the ignition parts market is that changing spark plugs has become a big-ticket job due to the lack of spark plug accessibility. More to the point, the lack of accessibility demands that the spark plug replacement be done right the first time. Spark plug wire replacements, for example, have become more of a necessity than an option because 100,000 miles of engine heat usually bakes wires firmly in place on vehicles like Fords Aerostar van, for example. This application commonly suffers misfires on the center cylinder of each cylinder bank because heat from the exhaust manifold cracks the center spark plug wires and boots. In most cases, the remaining wires are ruined during removal, so replacement with high-quality aftermarket wires is usually mandatory rather than optional.
To better state the case for routinely replacing wires along with spark plugs, modern OBD II engine-management systems manufactured since 1995 will record cylinder misfires and, when misfires reach a critical level, will turn on the orange light known variously as the Malfunction Indicator Light, "Check Engine" light or the "Service Engine Soon" light. (For more information on the check engine light, see Check Engine Light: Opportunity or Obstacle on page 36.) In modern parlance, replace with quality spark plug wires because you cant fool the misfire counter on modern engines.
Coil-on-plug (COP) ignitions are the most recent popular reconfiguration of the ignition system. As the name implies, the ignition coil is installed directly on the spark plug itself. In most cases, this "mini," pencil-thin ignition coil is connected to the spark plug with a rubber boot. Unfortunately, this boot often tears as the coil is removed from the spark plug. In other cases, water accumulating in the cylinder heads spark plug well has created a carbon track inside the boot that may altogether ruin the coil, boot and spark plug assembly.
So, will COP ignitions ruin ignition parts sales? At this point, the failure patterns on COP ignitions arent really apparent. But one thing is certain; were seeing engines with more cylinders being driven more miles and requiring more expensive replacement parts, all of which bodes well for todays ignition parts market.