94 Lumina APV

Hi folks!. I've got a 94 APV that won't pass emmissions. All readings are within specs except for the NOX. All fluids and filters were replaced and engine runs awesome. What I'm wondering does this vehicle have an air injection pump for the catcon?. Had a 1995 Camaro which also failed on the NOX readings which turned out to be the air injection pump for the catcon. Any input much appreciated. Thanks

EGR passages may restricted or plugged. EGR problems are one of the most common causes of NOX emission failures. I do not think your vehicle has an air pump.

Definitely no air pump. Indeed the EGR valve is the first likely culprit. '94 EGR valve is linear type like this www.avigex.ca/xport/egrlin.jpg (picture is for the 3.8)
Usually a failed EGR valve will pop a code, but if this is the original it would be an easy guess it is overdue, common issue.
Next in line is the catalytic converter itself....

Do you have a 3.1L or 3.8L engine? The EGR systems are different.

Do you have a 3.1L or 3.8L engine? The EGR systems are different.

It has the 3.1 litre. EGR has been replaced, ports were not overly plugged.