Except 300ZX

With engine stopped, visually inspect entire EGR system and clean as necessary. Replace hoses that are cracked or broken. Inspect EGR valve for signs of binding or sticking by moving valve diaphragm upwards with finger.

Fig 1: EGR System (200SX)
With engine running, check operation of EGR valve and thermal vacuum valve by placing finger on diaphragm of EGR valve and checking diaphragm movement.
With engine coolant temperature below "Closed" value, increase engine speed to 3000-3500 RPM (2000-2500 RPM on Pickup). EGR valve diaphragm should remain closed.
With engine coolant temperature above "Open" value, increase engine speed to 3000-3500 RPM (2000-2500 RPM on Pickup). EGR valve diaphragm should open and allow exhaust gas recirculation.
If EGR valve does not operate as indicated, disconnect EGR valve-to-thermal vacuum valve vacuum hose at EGR valve. Increase engine speed to 3000-3500 RPM (2000-2500 RPM on Pickup). Check for vacuum at end of disconnected hose.
On all except Maxima, if vacuum is present, check EGR or BPT valves. If no vacuum is present, check TVV valve. If vacuum is weak or not present, replace TVV. On Maxima, if there is no vacuum, check EGR valve. If vacuum is present, check TVV.