Ok. So. i went to go get my car smogged yesterday. Needless to say it failed. Would have been wayyyyy too easy if it passed. It failed because my NOx levels were close to twice the maximum. The guy at the smog station didn't speak the best English. But i think he was telling me i might have a problem with my EGR Valve. But he definitely told me he had no idea what the problem was. The car kind of idles weird. Sometimes it will be normal (round about 900rpm) Don't know if that is really normal. But anyways. Sometimes it will either go up to 1500 or sometimes even like 1900 rpms and the only way i can get it to go back down to normal is letting it idle for like 10-30 seconds. I was wondering if anyone had input. Plus i was watching when he was doing the smog check and it smelled rich in the test station. looked like the right side was running way more rich than the left though. The inside of the right pipe was legitimately wet. and when he gave it some gas during the test it kind of sputtered gas out of the pipe... or whatever it was. Anyways guys. Thanks for the responses

Getting the engine back to proper running condition is a process of checking all components to ensure they are working and up to spec. These engines connectors, the ones with the spring clip, are notorious for not being very weather resistant. Consequently moisture gets in and corrodes the connection. This leads to components working intermittently or failing altogether.

Step one is to pull the connectors and see if they are clean. These are the ones for the injectors, CAS, PTU, AAC, FICD, Air Regulator, MAF, TPS, Coolant Temp Sensor, as well as the EGR solenoid. IF there is any green corrosion on them it needs to be thoroughly cleaned. It's best to first scrape away any buildup, then apply a good quality contact cleaner ( my favorite http://www.mgchemicals.com/products/801b.html) and then also apply some dielectric grease to protect them.

Step 2 is to test all the components while the connectors are off. The measurements can be found in the manual http://www.300zx-twinturbo.com/cgi-bin/manual.cgi in the EF&EC section starting on page 178.

Make sure the timing is set to 15 degrees as well.

Also it's advisable to pull your spark plugs. Make sure they are the NGK ones that came with the car, not some after market plug. These engines are fussy. There are a couple others that will work, but in 99% of the applications the factory plug is the best. While the plugs are out, perform a compression test.

Your erratic idle could be several things such as intermittent spark caused by corrosion on the (CAS/PTU) connectors, poor coil pack (which is rare), AAC not working (common) or/and perhaps a vacuum leak.

The fuel pump pressure is also something that is good to test, not necessarily emissions related but should be done.

If all connectors are checked, components tested etc you will find the problem.

dude your f***ing awesome. thanks