1979 Ford FiestaFACTORY OEM SERVICE PROCEDURE

Idle Vacuum Valve

  1. Remove idle vacuum valve from connector on by-pass valve. Install a vacuum hose on small nipple of the valve and connect it to a 3-way tee. Connect another leg of the tee to a vacuum gauge, and the remaining tee fitting to the by-pass valve.
  2. Connect a vacuum gauge to intake manifold. See Fig 1. Start and warm engine to normal operating temperature.
  3. With engine at idle and transmission in neutral, disconnect large hose from large diameter port of idle vacuum valve.
  4. Using an external vacuum source, apply 3.5-4.0 in. Hg to large port of valve. Vacuum on gauge at by-pass valve should increase to within 3 in. Hg of intake manifold vacuum. If not, replace idle vacuum valve.
  5. Remove external vacuum source. Vacuum gauge reading should drop to 1 in. Hg or less. If not, replace idle vacuum valve.
Fig 1: Testing Idle Vacuum Valve
G09313213Courtesy of FORD MOTOR CO.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.