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:


  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

You May Also Like

Auto Pros Visit Interstate Auto Care, Madison Heights, MI

For Bill Nalu, business is more about fixing cars – it’s about connecting with people on a personal level.

In this episode of Auto Pros On The Road, Joe Keene and Jacqui Van Ham visit Bill Nalu at Interstate Auto Care in Madison Heights, MI.

Bill Nalu and his team of five skilled technicians at the Auto Value Certified Service Center pride themselves on what they call "aggressive hospitality." Because to him, the business is about more than just fixing a car. Family-owned and operated, the shop began with an attitude of first being in the service business; second an auto repair facility. The primary focus has been, and continues to be, the ever evolving needs and wants of every customer.

Can the US Electric Grid Power Electrify America?

The electric grid is aging, and its infrastructure is outdated.

Opus IVS, CARS Co-Op Network Join Forces

New partnership enhances diagnostic capabilities and strengthens mechanical programming skills to the repair professional.

Albemarle, Ford Form Strategic EV Production Agreement

Albemarle will supply 100,000+ metric tons of battery-grade lithium hydroxide for about 3 million future Ford EV batteries.

EV Battery Charging: What You Need to Know

As EV owners begin to look for qualified service shops, a charger will be an advertising beacon at your shop.

Charging EV car

Other Posts

AAM to Supply e-Beam Axles for Future Stellantis EV

The future program will feature both front and rear e-Beam axles that include AAM’s integrated 3-in-1 e-Drive technology.

Wrenchers Doubles Repair Tool & Equipment Offering

More than 25,000 lifts, tools, and equipment from 39 brands available online or by phone.

Myers Tire Supply Introduces MTS Xpresstm

The innovative solution to consolidate purchases and control inventory costs.

Experiencing What the Tool Industry Has to Offer

ETI held its annual ToolTech conference April 17-19 at the Hyatt Regency Tamaya Resort in Santa Ana Pueblo, New Mexico.

Sandia Mountains