my '84 300zx (z31) is having issues passing smog oddly.

I'm getting a high HC rating at idle, everything else passes fine.

everything gets spark and fuel, however, cylinder #4 seems to not be functioning properly, haven't gotten the compression tested yet; however removing the spark plugs to each cylinder effects idle, except #4

any ideas as to what would cause it to only have a high HC rating at idle?

it's getting 3800 when it should be 480.

 

You're on the right track, compression on #4 first,then if it's good you may not be getting a good spark to that cylinder which could be bad ignition parts. When last was car tuned?

 

i replaced the plugs, oil, and fuel filter last week.

#4 gets fuel and spark, but I don't believe it's igniting. my quick guess is the fuel injector isn't opening enough so it's not igniting at lower rpms(idle).

the idle will also stay at 600rpm and then randomly bounce up to 800rpm's and then back down. there is a 20 second-30 second gap in between the bouncing, but at 800rpm it will last 5 seconds then go back.

last time I had it at a shop, I was told my EGR is clogged, but I haven't figured out how to fix that problem either.

 

It's relatively easy to clean after removal as it's generally black sut caked up, so you can take a piece of wire to scrape out clogged ports.

 

know any good guides as to how to remove it?

 

Run a compression test before you start swapping ignition components. I had the very same issue develop on a VG30 in a Maxima. Compression test showed #4 was dead, so I start looking for signs of a blown head gasket. Couldn't find any. Finally took the car to an independent mechanic that specialized in Nissans who told me there had been an issue with VG30E heads developing cracks between the valve guides. Kills compression but doesn't involve the cooling jacket. I never tore the engine down to look at the damage.