Ignition

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A reasonable tune-up interval is 30,000 miles. Before cars had computers and fuel injection, a tune-up was an oft-repeated and artistic process, highly dependent on the skill of the mechanic. In modern vehicles, as the components wear out, various sensors tell the computer how to adjust the fuel to air mixture and other parameters so that optimum operation is maintained. This both compensates for, and lessens wear so modern vehicles can go a surprisingly long time and distance between tune-ups. These days a complete tune-up consists of nothing more than changing the spark plugs and a few other ignition components, changing some filters and checking the ignition timing.

You should have the engine compression checked when a tune-up is done and record the values on the chart. As time goes on you’ll be able to see if there’s any degradation and if large differences develop among the cylinders. A compression check is similar to a physician listening to your heart with a stethoscope.

Find out if you have adjustable valves. If you do, they should be adjusted every 15,000 miles. Check your owner’s manual or ask the dealer. Most modern cars have hydraulic lifters which are self-adjusting. Make a note of your valve type in your log.

Replace the spark plugs after about 30,000 miles. Some newer vehicles may have platinum plugs that are reputed to be good for 100,000 miles. Dr. Dipstik wonders if it will be possible to get them out after 100,000 miles and many years of exposure to the elements. If Dr. Dipstick had those babies in his car, he would pull them out after 50,000 miles and at least have them looked at. That way there will probably be a good chance they’ll be removable at 100,000 miles.

If you have a distributor, replace the cap and rotor after 30,000 miles. Many cars have distributorless ignitions and nothing further need be done to those. Make a note of your distributor type in your log.

The oxygen sensor should be replaced, but not when the reminder light comes on. It should be replaced when it no longer works. The oxygen sensor is important to the operation of the pollution control system. Most cars have an annoying red or amber reminder light that comes on about every 30,000 miles that tells you to replace this $100+ component. Dr. Dipstik has a hard time agreeing with those who feel this is an intentional scam perpetrated on an unsuspecting public, but he’s beginning to lose his resolve as he becomes older and weaker.

If your car passes the annual emissions inspection in your state, the oxygen sensor’s function has been checked and found OK. If you live in an area that doesn’t have an annual emissions test, consider having the emissions checked about once a year anyway. It’s a good way to have an early warning of any impending problem.

You are left with the problem of turning the accursed reminder light out. There really is a secret switch under the dash or the hood that does the job. Some lights are turned out by momentarily disconnecting the wire running to them. Most service stations have a book that tells the location of the reset switch. A nice mechanic will tell you where it is, usually for a small token payment equal to the cost of replacing the oxygen sensor.

You should check the water in the battery, (if you have the older type) about once a month in warm weather and about every 2 months in cooler weather.

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