Tech Tip: Voyager Basics - Loss of Speed Control

Tech Tip: Voyager Basics – Loss of Speed Control

A simple malfunctioning vacuum valve on some 1996 to 2000 Plymouth Voyagers can result in a loss of more than 5 mph while climbing a grade with the speed control engaged. The actual cause of the problem could be a leaking check valve in the battery tray/vacuum reservoir assembly.

With all the tasks we attend to in our everyday lives, it’s nice when something comes along to make at least one chore a little easier. In this case, our vehicle’s speed control makes long-term driving much easier. Without speed control, long road trips would be more tiring for the driver and, for those of us suffering from lead-foot syndrome, would probably become expensive from speeding tickets.

Here’s something interesting: Instead of becoming obsolete due to increasingly high traffic congestion, speed control system technology is becoming more advanced. Soon, vehicles will be equipped with adaptive speed control. For example, two innovative companies are developing forward-looking radar, which allows your automobile to follow the vehicle in front of it while continually adjusting speed to maintain a safe distance.

Anyway, no matter how great new automotive technology gets, something so basic as a vacuum leak can sideline any sophisticated system. In fact, a simple malfunctioning vacuum valve on some 1996 to 2000 Plymouth Voyagers can result in a loss of more than 5 mph while climbing a grade with the speed control engaged.

The actual cause of the problem could be a leaking check valve in the battery tray/vacuum reservoir assembly. The check valve traps vacuum in the reservoir to allow the speed control to work under low manifold vacuum conditions. The valve may become contaminated and cause it not to seal intermittently. This can cause a loss of vacuum to the servo while driving on a long uphill grade. The following details will outline how to test and repair this problem:

Diagnosis:

  1. Verify that the ignition switch and all the accessories are turned off.
  2. Disconnect the negative and positive battery cables.
  3. Remove the battery hold down (Figure 1).
  4. Remove the battery from the vehicle.
  5. Disconnect the vacuum line that connects the vacuum reservoir with the speed control servo.
  6. Connect a hand-held vacuum pump to the small, top nipple on the vacuum reservoir, and apply 20 inches of vacuum.

• If the vacuum leaks down more than two inches in five minutes, perform the Repair Procedure. If not, look for other sources of vacuum leaks.

Repair Procedure:

  1. Remove the nut and two bolts from the battery tray, Figure 1.
  2. Remove the speed control servo-attaching bolt from the battery tray.
  3. Disconnect the vacuum lines from the battery tray vacuum reservoir.
  4. Remove the battery tray from the vehicle and discard it.
  5. Connect the vacuum lines to the revised battery tray vacuum reservoir (Mazda part number – 04716740AB).
  6. Attach the speed control servo to the battery tray. Tighten the bolt to 50 in. lbs. (6 Nm).
  7. Install the battery tray. Tighten the nut and two bolts to 140 in. lbs. (16 Nm).
  8. Install the battery. Tighten the hold-down clamp bolt to 180 in. lbs. (20 Nm).
  9. Connect the positive and negative battery terminals.
  10. Return the clock and the radio to their original settings.

The last step is a very important one. The first two things that customers notice when they get back into their car are the clock and radio settings. If those two basic things are taken care of, they’ll be more likely to appreciate your professional repair job. Isn’t it funny that no matter how sophisticated these systems and your knowledge of them gets, it’s still the basic things that make the biggest difference?

Written by ALLDATA Technical Editor, Rich Diegle. Rich is an Advanced Engine Performance Certified and ASE Master Technician with an Associate of Arts degree in automotive technology and 22 years of dealership and independent shop experience.

For additional information, visit www.alldata.com.

You May Also Like

We Want To Know: Where Do You Buy Your Parts?

Your honest and anonymous responses today will help us provide better information to you in the future.

As important as which parts you select may be the question of where you find them. We're interested in finding out where shops get the parts that go into their repairs and would appreciate your comments.

From time to time, ShopOwner conducts surveys to help us guide our editorial direction and help our partners determine what's important to you, our readers. These are very important studies, because they allow you to respond anonymously and honestly. We need your help!

Do EVs Require Special Brake Pads?

Proper brake pad selection is crucial for EVs to ensure consistent stopping power and long pad life.

Five Tips for your Next Wheel Bearing Job

These practical tips are designed to save you time and frustration, ensuring a smooth, noise-free outcome for your customers.

Sun Auto Tire & Service Acquiring Caliber Auto Care

The company is acquiring 33 Caliber Auto Care locations throughout the state of Texas.

Steering Angle Sensor Service

Ninety percent of the time when a steering angle sensor code is active, it means the sensor needs to be calibrated.

Other Posts

Honda Launches Fuel Cell Electric Vehicle in Ohio

Production of the 2025 CR-V e:FCEV fuel cell EV begins at Performance Manufacturing Center in Marysville, Ohio.

Schaeffler Showcases Hydrogen Electrolyzers and Fuel Cells

Schaeffler also is demonstrating its progress toward the commercialization of green hydrogen.

Bosch Releases 87 New Part Numbers in June

Bosch’s new part numbers cover 318 million vehicles in operation across North America.

Educate Your Customers Utilizing AI

Discover how to generate quick, accurate explanations for repair orders and estimates, boosting your shop’s credibility and customer trust.