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Q I have a problem with my 1997 Mazda Miata. The "check engine" light has been on for 3,000 or 4,000 miles, but the car has been running fine and getting good mileage -- 30 to 36 miles per gallon.

The other day I started it, and it sounded rough, as though it were missing on one cylinder, and there was a clicking noise like a rocker arm tapping. Can I hurt my car by running it with a bad catalytic converter?

A Hundreds of faults could trigger the check-engine light. Why do you suspect a bad catalytic converter? If it were plugged or restricted, the exhaust gases from the engine would be choked and restricted, causing a significant loss in power and economy, and overheating the converter. Why not start by having a shop check for the specific fault code with a scan tool? This is exactly what OBDII on-board diagnostics are designed for.

As for the tapping noise, it could be caused by anything from a loose spark plug or arcing ignition wire or coil, to a stuck valve or a worn lifter, cam or rocker.

Q How do I remove an electric-window motor from my 1996 Ford Windstar?

A Find the one accessible window regulator/motor retaining screw and the dimples in the inner door frame directly in front of the two hidden retaining screws. Drill out these dimples with a half-inch drill bit, making sure the wiring harness is clear. Remove all three retaining screws, then with the window retained in the full up position, push the motor assembly toward the outside to disengage it from the regulator gear.

Q Does it damage an automatic transmission to slip it into neutral to coast down long stretches of road -- or short ones for that matter? I don't turn the engine off because I've heard they have transmission coolers that don't work if the engine's off. But, I also heard that this still can damage the transmission even with the engine running. I was told I was going to spend many dollars later just to save pennies on the current tank of gas.

A You were told correctly -- at least about the potential savings. Modern electronically controlled fuel-injected engines burn very little fuel while decelerating, meaning closed-throttle coasting. Fuel-injector pulse widths are minimized, so the difference in fuel consumption from deceleration to idle is minimal. With that said, it probably won't hurt the automatic transmission to be shifted into neutral while coasting, then shifted back into drive -- but it's not going to do it any good, either.

A far more important part of your question is the "turn the engine off" issue. Never shut the engine off with the vehicle in motion -- you will quickly lose the benefit of power brakes and power steering!

Many motorists still believe that if the engine stalls while moving, the steering locks up and the brakes don't work.

This is absolutely not true, but both systems will require far more physical effort to operate because of the loss of power. To experience what this feels like, park your vehicle, shut the engine off, then push the brake pedal a half-dozen times to use up any residual vacuum or hydraulic assist. Now, how hard do you have to push to engage the brakes?

Like I said, never shut the engine off while driving, and more important, remember that, with the engine not running, the brakes and steering still work -- you just have to work at them much harder.