93 300zx Rough Idle/dies ASAP HELP!!!!

[rewolf24]

93 300 zx has had a rough idle for a while. I noticed it when sitting at a stop light, rpms stay between 1000 and 500. Engine will run fine above 1000 but when i come to a full stop rpms drop down to 500 and jump back up. At a stop light engine runs fine for a second but rpms flicker down to 500 and right back up to just under 1000 almost as if the engine is cutting out. Once i give it some gas it idles fine. Just recently I was going to sell the car but right as i pulled into meet the guy at the bank engine stalled out on me right as i pulled into the parking lot. This has happened before except the last time it died it sat for a few minutes and i was able to start it right back up as if nothing happened. This time it would not start. Engine would crank but it sounded like a fuel problem. I finally got it to start again after i got it towed to my house. I hooked up a fuel pressure tester to it and there were no problems on that end. I did notice while revving up throttle the rpms would go up and down at a certain throttle position. I know the fuel injectors are the "old style" could this have anything to do with it? I did check the codes from the unit in the floor board on passenger side but nothing came up. Light blinked code 55 which means nothing detected. Could any components that control the engine idle be causing an issue like this? The engine doesn't always have a rough idle. Sometimes it runs fine other times the rpms keep flickering down to 500. I know this is a loaded question but what are all the possible components that could cause this to happen? I need a hit list so i can check everything. This car is a convertible N/A automatic but still is very fun to drive. Easy car to sell if it runs right.

[Ziggy1621]

Welcome to NICO!

I would need more info on the 'not being able to start' issue, but the fluttering idle is probably because your IACV isn't set (Idle Air Control Valve).

Try this: http://www.nicoclub.com/archives/adjust ... level.html

[DCaff300ZX]

The Online Service Manual has detailed tests for different problems related to the idle circuit...fresh fish for the day:
http://300zx-twinturbo.com/cgi-bin/manual.cgi

[canadian booster]

i like to start with the basics :
air - make sure clamps aren't loose, there's no boost leaks, etc
fuel - is it getting any? you tried a fuel pressure thingie, i have one too, pretty handy
fire - sparkplugs been changed ever? n00bs usually change 4 out of 6 because the last 2 are a pain, maybe they're old or maybe even the coil pack isn't plugged firmly onto the sparkplug

if you're good there, try things like the IACV, or even dump some SeaFoam into your gas tank and clean that puppy out, pour some into the oil also, drive around, then change the oil with new stuff and new filter (this erased my lifter tick)

crappy idle is hard to troubleshoot, especially on a 55 code