LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Pontiac >> 1988 >> Fiero Formula, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> EGR System >> Component Testing >> Negative BACKPRESSURE EGR Valve
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Negative BACKPRESSURE EGR Valve

  1. With EGR valve in vehicle and engine off, disconnect EGR valve vacuum signal hose. Connect vacuum pump to vacuum signal tube and apply 10 in. Hg vacuum. EGR diaphragm should move up and remain up for 20 seconds.
  2. If diaphragm does not stay up for 20 seconds, replace EGR valve. Using an assistant, again apply 10 in. Hg vacuum to signal tube. Have assistant immediately try to start engine. Observe diaphragm for movement.
  3. If diaphragm moves to a seated position (valve closed) during cranking and initial starting, EGR valve is functioning properly. If diaphragm did not move, clean or replace EGR valve.
  4. If EGR valve is not in vehicle, connect a short section of hose over the EGR valve seat. Apply 10 in. Hg vacuum to vacuum signal tube. EGR valve should open. If valve does not open, clean or replace EGR valve.
  5. With vacuum still applied, plug intake port of valve with thumb. Apply suction (with mouth) to hose connected to EGR valve seat. The EGR valve should close immediately.
scientia non olet · About LEMON Manuals