My Acura Legend has about miles on it I still...

Dear Car Talk

Dear Car Talk | Jan 01, 1994

Dear Tom and Ray:

My 1988 Acura Legend has about 67,000 miles on it. I still love the car, but there is one problem. In wet weather with the cruise control on, the gas pedal begins to move up and down as if an invisible foot is playing with it. This causes the speedometer to vary by several miles per hour either way. It gets worse in hilly terrain, but only when it's damp or raining. My mechanic is stumped. Can you help me?

TOM: Ah, yes. The "Invisible Foot Phenomenon." IFP, as we say in the business.

RAY: It's certainly possible that moisture is somehow interfering with the electronics of the cruise control. But I'll bet the problem is more basic than that.

TOM: I agree. It's more likely that the moisture is making the engine itself run poorly, and that the "Invisible Foot Phenomenon" is just the cruise control trying to make up for the engine's poor performance.

RAY: You're probably doing the same thing with your foot, but you don't realize it, because unlike the cruise control, you're not trying to keep the car at exactly 55 miles per hour.

TOM: When a car runs poorly in wet weather, it's usually because moisture is "stealing" some of the electricity needed to make the spark. So the first things I'd check would be the spark plug wires and the distributor cap. Those are the cheapest, and most likely causes of this kind of problem. From there, I'd go on to check the other parts of the ignition system.

RAY: And if you're satisfied that the ignition system is not being affected by the moisture, ask your dealer to try replacing the electronic portion of the cruise control system. If that solves the problem, pay him for the part and drive away happily. If not, have him take it out, make an appointment with a paranormal phenomena specialist, and take a more serious look into the Invisible Foot theory.

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