I just went thru this on my 93 n/a. How far did you drive, before you when to get the emissions test? What brand of plugs are in the engine? Do you have cats on your "77"? When was the last time you replaced the PVC valves? Do you have the emissions test levels? What is the standard for your car and what levels did your car fail at?

 

When I failed my emissions test. I was running with Bosch plugs also, and only drove my car about 5 to 6 miles to test station. My HC and CO were 4 times the limit (running rich fuel mixture). This is what I did, and it passed. Replaced the pluges with NGK pluges for my car, you can get them at the Nissan dealer. I ran my car for about an hour on the highway to get the cats hot enough I changed the PVC valves, crank case ventilation is sometimes re-routed back thru intake, they don't cost that much. I changed my oil, oil filter and air filter. It passed way below the standard limit. I was told that it's real important to get the car hot enough and have the right plugs. I didn't use it but at PEP BOYS autoparts, they have a bottle of stuff that you mix in your gas and run a tank full through your car and they guarantee it to pass. It's called PASS EMISSIONS TEST. Good Luck, let us know how you make out.

 

It's very possible that your airflow meter has been adjusted. If you take off the black plastic cover, there is a hex bolt head, I beleive on the left. This can be loosened, and the flap can be adjusted, altering the fuel mixture. It is a very popular way of getting a little more pep out of the z's.

They came from the factory with a dab of epoxy, or something similar to, on the bolt. Chances are, if there isn't any, it's been adjusted.

You should be able to tell which way to adjust the flap pretty easily. Be carefull, only adjust by a tooth or two at a time.

Phil