Anti-AFTERBURN Valve

Disconnect the air suction lower hose from anti-afterburn valve. Start engine and allow to idle. Place finger over tube. Quickly raise engine speed to 3500 RPM and close throttle quickly. If there is no vacuum, go to step 5).
If vacuum is present, check for voltage at the anti-afterburn control solenoid valve Yellow/Black wire. If no voltage is present, check the speed sensor. See Trouble Shooting in this article.
If voltage is present, disconnect vacuum hose number 31 from the anti-afterburn valve. Check for vacuum. If no vacuum is present, locate restriction or blockage and retest.
If no defects are found, replace the anti-afterburn valve and retest. If vacuum is present, replace the anti-afterburn valve and retest.

Fig 1: Testing Anti-Afterburn Valve Use finger to check for vacuum.
Jack up the front of the vehicle and support with safety stands. Block the rear wheels and set the parking brake. Place the shift or selector lever in second or 2 position and accelerate. Release the throttle suddenly and check for vacuum during deceleration above 10 MPH.
If there is vacuum, system is okay. If there is no vacuum, check for voltage at the anti-afterburn control solenoid valve above 10 MPH.
If there is voltage, check speed sensor. See Trouble Shooting in this article. If there is no voltage, disconnect vacuum hose number 31 from the anti-afterburn valve and check for vacuum above 10 MPH.
If there is vacuum, replace the anti-afterburn control valve and retest. If there is no vacuum, disconnect the vacuum hose number 30 from the anti-afterburn control valve.
If no vacuum is present, check for leaks or disconnected hose and retest. If vacuum is present, replace the anti-afterburn valve and retest.