[mrnickleye]

Also, the egr system is very prone to plugged passages.

quoting myself:

High NOx & Testing the EGR System

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High NOx is an indication that the EGR system is not working properly. Very possible that the vacuum hoses aren't hooked up properly, or the passages are plugged with carbon, and not allowing exhaust gasses to flow into the intake to control the NOx.

The EGR valves are very tough, and usually don't go bad. They could be plugged up with carbon. The transducer (back-pressure sensor) above the valve does go bad.

You can check some of this out yourself by un-plugging the vacuum hose to the EGR valve while the engine is idling, and use a longer piece of vacuum hose (keep it in your toolbox for future uses) to plug onto the EGR and suck on it with your mouth.

If the EGR valve is working, and the passages aren't plugged, the engine idle will fall right off, and possible kill the motor. If this happens, then your transducer is likely bad. Dealer only part.

If you can't hold the vacuum with your mouth (cause air comes thru) then the valve diaphram is bad, and the valve won't open.

If the idle does not fall off, and the valve seems to hold vacuum, (suck and release quickly with your finger on the valve, you should feel it snap shut), then you can remove the metal tube from the valve to the intake manifold, then try testing again. If you get loud exhaust coming out of the valve, then the passages are plugged in the intake manifold, and must be cleaned out.

The passages may be plugged before the valve, in the EGR cooler. Hope not, as it will be a bitch to remove the cooler and clean it out. Check by removing the EGR valve and starting the motor to hear if exhaust comes out the hole.