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Re: Cruise Control drops off...Help
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Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Wed, 11 Dec 2002 13:14:38 Share Post by Email
In Reply to: Cruise Control drops off...Help, Chaz, Wed, 11 Dec 2002 00:02:50
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I would go first with a vacuum hose leak.
The cruise control has a vacuum actuator that pulls a chain, pulling the gas pedal open. The more vacuum, the more the actuator pulls the throttle open. There is a vacuum pump mounted on the left front fender, and that (electric) pump is controlled by the cruise control. What usually happens is that a hose develops a crack. Everything is OK when you first engage the CC, because the throttle is already in the right place. But over the next few seconds, the spring tries to make the throttle closed, so the pump runs faster to keep it open. But with a vacuum leak, eventually the pump is running flat out, but it can't keep up with the leak.

With minor leaks, the car will hold speed, sort of, on level roads. But hit a hill, or anyplace where more throttle is required, and the speed drops off.

Check ALL the hoses for cracks - usually where they connect to a nipple, but also where they go through holes in the bulkhead. The line runs from the pump to a vacuum switch (sets base boost with CC engaged) and then through the firewall to the vacuum actuator. The usual place for the hose to crack is at the pump, because the underhood temperatures are pretty bad for rubber. It may also be at the actuator under the dash (remove left speaker grill and look in), but less likely.



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