Badin vs. Coldwater
Zoo mommies and babies
2009 China Fashion Week
The case of the wet ignition system
Saturday, February 07, 2009
Wheels:
An e-mail from Keith in Englewood says, "My 1997 Ford Aspire (made by Kia Motors) has been plagued by a problem that three mechanics failed to fix. Symptoms: Every time it rains or even gets very humid here in southwest Ohio, the engine putters/misses/loses power. This problem doesn't present
itself when the air is fairly dry.
The following have been replaced, to no avail: distributor cap, spark plug wires, spark plugs, EGR unit, air filter, both the upstream and downstream oxygen sensors and maybe some others I've forgotten. I've also tried adding a fuel injector cleaner additive to the gas.
The only thing I can do to help alleviate this somewhat is to let the engine warm up completely and idle for about 15 to 20 minutes. It gets better, but doesn't completely stop missing/sputtering. One mechanic found a code (No. 4 cylinder misfire), but he had no solution, and the check engine light stays on. I can't afford to spend a lot on the fix for this, but I'd like to keep the car because of the 38 mpg aspect! Your consideration in this is greatly appreciated."
Halderman: Whenever there is a problem with the engine not running correctly when wet, it is almost always due to a problem in the secondary ignition system. It appears that everything in the secondary ignition system has been replaced except the ignition coil. This, plus being sure that all of the replacement parts are in good condition and good quality, should cure the problem.
Wheels: Why does moisture affect the ignition system?
Halderman: Moisture on spark plug wires increases the capacitive resistance. What this means is that a higher voltage is needed to cause an arc to be created at the spark plug.
Many vehicle manufacturers use rubber coverings over the distributor cap to help prevent the moisture from affecting engine performance. Because moisture on the ignition components can effectively reduce the spark energy to the spark plugs, it is very important that the spark plugs have the specified gap.
As a spark plug wears, the gap between the center electrode and the side electrode increases. When this gap increases, it requires a higher voltage to arc across the gap.
Also, for best results, use factory ignition parts or those from a well-known national company.
When many professional service technicians see low-cost aftermarket parts have been installed, such as ignition components, and there is still a problem, they immediately replace them with original equipment or good equipment-quality parts. In most cases, the problem is solved.
Aftermarket parts are not required to be tested for durability like original equipment parts, and that is one reason for the cost difference.
James D. Halderman is the author of 12 automotive textbooks and is an ASE-certified technician. Submit questions to him via e-mail at jhalderman2@juno.com, or write him at Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
