Super High Idle

[Thornajal]

Howdy all, just picked up a 300zx and noticed that at idle in park it idles at around 2200 RPM. The security light is flashing on the dashboard so after some Digging around I found that it might be the theft sensor going bad, so I removed the passenger seat and unplugged the theft sensor turned her on and she idles at 1500 RPM now but has a sputter every 2-3 minutes. Now my question is do I just leave the theft sensor unplugged? or is there something else that I need to do?

[Thornajal]

*UPDATE* ok it's now back to idling at 1900 RPM, this is an automatic btw. so apparently the security light blinking while it was on isn't causing it completely but it helped for a bit.

[t.mcginley.jr]

I'm surprised the idle is affected by the security at all. When I was having problems with the factory security (headlights/blinkers flashing randomly) I just unplugged the security control module by the ECU and it's been great ever since. They get buggy after a while.

As for the high idle, did you check for codes yet? Could be a number of things... bad MAF, bad or uncalibrated TPS, bad injector(s), bad IACV, etc.

http://www.nicoclub.com/archives/nissan ... ostic.html

[Thornajal]

no codes of any kind, sorry forgot to mention that. I read somewhere online (go figure) of some one having high idle issues and disabling the theft device helped them. I still need to figure out why it Was flashing. or Do I even to bother plugging it back in?

[Thornajal]

Update* Ok I still don't know if I should even bother plugging the anti theft back in, BUT when it starts cold it Idles in the perfect range, once it gets up to operating temp is when the Idle goes up to 2K, That makes me think it's got to do with either the EGR, or Idle Air Control unit... Thoughts anyone?

[Thornajal]

OK after triple checking every thing the EGR Tube going from exhaust to the valve is pinched, not 100% closed but pretty freaking close. got the part ordered i'll let yall know if that solves it 100%, Still would like any ones input on if I should even bother plugging the anti theft box I unplugged to get the security light to turn off.

[KornFlakeZ]

While your working on the car i would remove the IACV and give it a good clean with some carb/choke cleaner. After a while, carbon deposits make the valve sticky and make your car not idle right.

[t.mcginley.jr]

While your working on the car i would remove the IACV and give it a good clean with some carb/choke cleaner. After a while, carbon deposits make the valve sticky and make your car not idle right.

+1, take your IACV off the back of the plenum and spray the insides down with carb/TB cleaner to get the carbon deposits off. Before putting it back on spray the spring/valve with some WD-40 or equivalent.

[Thornajal]

Thanks for the Tip! last time I worked on a car from the 80's it was a Pontiac firebird and that thing had some terrible gremlins, I'm hoping this Z won't be the same haha, I'll update again once the tube comes in and I clean out the IACV. I'm so glad I bought the Haynes manual for this when I picked it up

[huntinman13]

I was having high idle problems as well. Cleaned the IACV and I had a spring loose in the air regulator. Give that a shot and check all the vacuum lines.

[Thornajal]

I was having high idle problems as well. Cleaned the IACV and I had a spring loose in the air regulator. Give that a shot and check all the vacuum lines.

I've checked about half the vacuum lines and man that's a task haha, some look like they are in "ok" condition, any one have a place to order new ones or do I need to Fab them like I had to for the FireBird?

[t.mcginley.jr]

It's way easier to just buy 10 feet of hose and make your own. The smaller ones are 4mm hose and the slightly larger ones are 6mm vac. hose. I order silicone hose off ebay by the foot. 10 feet is usually $20 or less shipped. Just search "4mm silicone vacuum hose", etc. Pull the old ones of and cut a similar size one off the new hose.

You can also buy a boost leak tester (http://www.z1motorsports.com/product_in ... ts_id=1867) for like $24. You plug it into the rubber t-pipe in place of the MAF and pressurize it with an air compressor. Fill it with like 10 lbs of pressure and you will literally hear any vacuum leaks hissing away.

[DCaff300ZX]

Definitely check the IACV and beyond making sure it's working/clean, be sure to check the large hose to the balance tube as it can easily split from age and will cause a leak that can affect idle and vacuum. Checking/replacing vacuum hoses is a great idea as well while you are there.
Your coolant temp sensor connection (mounted top coolant hardline on engine) will also most likely have corrosion, and this bad connection can trick the ECU into thinking the car is too cold and needs to idle up...clean that thoroughly.
Next up is checking all of your connections at the injectors, CAS, CTS/PTU (check BOTH large connectors) and IACV for green corrosion, which all must be cleaned and di-greased.
Hope this helps!

[Thornajal]

Amazing replies guys thanks I have a lot of work cut out for me but i'm excited to get into it! I think I have a fuel leak, the stupid previous owner zip tied the rubber fuel lines coming from the fuel pressure regulator to the main Collant hose it after years the zip ties and hi temps have cut / burned a hole in those lines >_>, been looking for replacements but haven't had luck yet.