Late oil change not to blame for shaky start

By Paul Brand

Last update: May 24, 2006 - 10:45 PM

Q When I recently started my 2000 Mercury Sable, I realized that the "emissions light" began flashing and the car seemed to be shaking a little. After I parked and restarted the car, the light stabilized and the shaking subsided. What might cause this? I plan to take the car on a road trip that could amount to 900-plus miles over four days, and I am wondering if this will be a problem. The car will get an oil change before I leave. Is the problem related to the need for an oil change? The car has 73,000 miles and is about 50 miles overdue for an oil change.

A The "check engine" or "emissions" light illuminates when there's a malfunction with the engine management system. I think the engine misfired in one cylinder upon start-up, causing the shake and triggering the light. It had nothing to do with an oil change.

Have the oil changed at the dealer or independent shop equipped with a diagnostic scan tool that can read the trouble codes associated with the emissions light coming on -- this should point you and the shop to the cause of the misfire. A typical cause is a leaky fuel injector or fuel pressure regulator that dribbles raw fuel into the engine, leaving one or more cylinders flooded at the time of start-up. Often, just a few moments of running will clear the flood, allow the engine to smooth out, and turn off the emissions light. The fault code will remain stored in the computer's memory.

The engine in your Sable features coil-on-plug ignition, meaning there is an individual coil on top of each spark plug for each cylinder. A weak coil might cause the misfire. And remember: The federal emissions warranty covers the computer and catalytic converter for eight years and 80,000 miles.

Q I have a 1988 GMC pickup with 188,000 miles on it. The truck has electronic ignition. I replaced the distributor cap and rotor a few years ago and now have had to do it again. What causes "carbon tracking" in the distributor cap?

A With that many miles on the truck, probably a worn distributor shaft and bushing. This allows the distributor shaft to wobble as it rotates, increasing and decreasing the air-gap between the rotor contact point and the terminals inside the cap. In severe cases, the rotor tip can hit the terminals, causing wear and even breaking the rotor. Carbon tracking can happen as the spark from the tip of the rotor arcs inside the cap because of the increased air-gap.

Pull the cap off, grasp the rotor and try wiggling it. If there's significant play in the shaft, it's time for a replacement distributor assembly.

If there's no play, check for moisture inside the distributor cap. Because water is such a good electrical conductor, the spark from the rotor can arc to ground through the moisture, leaving a carbon track on the inside of the cap. Cleaning and drying the inside of the cap and applying a light aerosol moisture-dispersing spray might help prevent carbon tracking from reoccurring.

Q I just bought a 2006 Chrysler Town & Country minivan. I plan on keeping it for up to 10 years. There is a three-year warranty for rust on the van. I don't know if I should have it rustproofed or not. I have read that the benefit of weather rustproofing is doubtful.

A I still believe in professional rustproofing on any vehicle that must survive 10-plus years on Minnesota's salty roadways. Granted, today's automobiles feature far better materials and construction methods that have reduced their vulnerability to rust, but if it's made of ferrous metal it eventually will rust. Rustproofing's relatively low investment and warranty seem like an inexpensive insurance policy to me. We had our '96 Tahoe rustproofed when new, and it remains rust-free 10 years later.

Don't forget though, washing and keeping the vehicle clean are the primary elements in preventing rust: Wash the vehicle as often as you can in winter.

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