Dear Tom and Ray:

Last summer, my family and I loaded up the '91 Taurus and went for a drive in the mountains. When we got to an altitude of 8,000 or 9,000 feet, we seemed to lose more and more power, and about the only way to maintain speed was to floor it until we got into passing gear. I assume the car was suffering the effects of oxygen deprivation. Is there a simple adjustment that I can make to the car when we drive over the mountains again next year? -- Mark

Tom: Well, I suspect that the only adjustment you could make would be to go around the mountains instead of over them, Mark.

Ray: Your car has a Manifold Absolute Pressure (MAP) sensor, which automatically adjusts the fuel mixture to compensate for altitude changes -- and the relative lack of oxygen at higher altitudes.

Tom: The problem is that it can only adjust so far. Once you get up to 8,000 or 9,000 feet, the air is getting pretty thin. And my guess is that the car just doesn't have as much air as it would like at that altitude. And when there's not enough air, the engine-management system cuts back on the gas. And when there's less air AND gas, you get what? Less power!

Ray: Keep in mind, this car was not exactly "over-powered" to begin with. Plus, you're also asking the engine to do its maximum amount of work under those circumstances. You've got the whole family in the car, and you're climbing a mountain. So if that's the only time you've noticed the problem, I suspect it's an "environmental" problem rather than a mechanical one.

Tom: Of course, it's also possible that you've got a clogged filter. If your fuel filter or air filter is clogged, for example, the car would demonstrate the same symptoms under maximum load. So have that checked. But my guess is you're just going to have to slow down and smell the fir trees next year, Mark.

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© 1998 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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