Hi guys, new 300 owner here, I had a 200sx S13 for about 4 years so im not a complete newbie but here goes.

 

My car is idleing very high at around 1800RPM but not all the time, cold start it idles high (as expected) at about 1800 if i leave the car idling and don't drive it takes a few mins but then eventually warms up enough and the idle drops down to around 800rpm but if i drive the car more often than not the idle then sticks at about 1800rpm it doesn't hunt or anything stays at a constant 1800rpm.

 

Occasionaly the idle does go back down to 800rpm but this is proberbly 1 in 10 times I use the car.

 

Sometimes i've also noticed idle changes when turning off the lights (HID) the car also has a Mines ECU Map (not sure if this is relevent)

 

I have searched and I have read some posts about high idle but thought I would post this aswell.

 

any help would be great thanks

Hi and welcome....

 

there are a number of issues that can cause issues with high/erratic idle.

 

so from easiest first....

 

check the connector for the ecu temp sender unit (top water pipe, the one with two spade connector), make sure its clean (while your at it undo, clean and reseat any other connectors you can find, take care as some are hard to get the clips undone and mat be brittle, include the battery).

check for fuel leaks on the fuel rail, the rubber hoses often leak.

don't forget the MAF (under the nose panel), the filter could also do with a check, clean /replacement.

the IAA is a regular for needed in a clean or adjustment... but there are other setting that need to be checked as well.

 

there is a guide to resetting the Throttle Bodies (really worth doing, you don't know who's been pissing around with it before you)

the TPS needs to be checked (around 0.45 volts), the timing should also be checked (15 tdc). then set the idle with the IAA adjustment.

 

nothing wrong with making sure the engine is earthed properly and has regular oil changes (15W40 semi), fuel/oil filters and the right plugs (PFR6B-11C)

 

all this stuff can be found in the techFAQ section or search in forum, you'll find link to other sites with info.

 

get yourself a diagnostic system (Conzult has a free one) with the adaptor/connector (£15 ebay), it will make things easer.

 

a few that might help:

 

http://z32.wikispaces.com/

http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?cat.8

http://www.twinturbo.net/nissan/300zx/tech/tech.aspx

Oh, I didn't mention Boost vac leaks... always worth getting/making a plug to do this check as well (goes in place of the MAF).... a real pain to find sometimes. :)

 

I hope that's enough to be getting on with...

 

Also try unplugging the O2's (if the other stuff doesn't fix the problem).

Oh, I didn't mention Boost vac leaks... always worth getting/making a plug to do this check as well (goes in place of the MAF).... a real pain to find sometimes. :)

 

I hope that's enough to be getting on with...

 

Also try unplugging the O2's (if the other stuff doesn't fix the problem).

 

I know for a fact the 02's was almost brand new when i bought them, dont't think it would be that mate - (It's my old car ;))

thats cool gives me some stuff to look over thanks!

Oh, so ShaneKerry has my old cars sister does he :) ?

Had same problem with mine, water pipe temp sensor having a bad connection can cause it.

 

Try these...

 

http://www.aus300zx.com/forum/showthread.php?t=274507

 

http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?content.335

Mine was kicking at about 3-4k somewhere not long along and found it only happened in the rain as the maf was getting wet

Mine was kicking at about 3-4k somewhere not long along and found it only happened in the rain as the maf was getting wet

 

Had similar thing with mine in the rain too and at 3000rpm. only while driving. no erratic idling.. wonder if need to have some sort of a splash guard of the large intake to stay dry!

just been out and messed about with it, unplugging the yellow sensor at the front made no difference to the idle speed but made the engine fan kick up to 100% unplugged an o2 sensor and the idle went down and then hunting around plugged back in again and idled up at 800rpm and stayed there, gonna drive around a bit today see what happens as usualy when it idles normally as soon as you drive just fires back up again!

just been out and messed about with it, unplugging the yellow sensor at the front made no difference to the idle speed

 

right, so you're talking about the 2 pronged ecu temp sender unit..

 

the unit sends information back to the ecu as the temp changes so just unplugging it without further information isn't any help...

 

did you warm the car up first and them unplug it?

did you unplug it and then start the car and let it run?

 

when you "messed about", who exactly were you messing about with?? :)

 

since we're not there we really need you to tell us what you have done so wee can rule that out now....

 

either get someone local with conzult (or datascan or other software) or get one on the cheap units form ebay, that will at least give you an accurate reading for what the ecu sees with Temp, TPS, air flow, injection time and a single.

readout for O2.

These may not help to solve the problem but will help to rule stuff out and narrow it down.

Sounds like the neutral switch to me, a common problem.

well I seem to have solved the problem somehow, I warmed the car up let it idle was sat at about 1800rpm and was going to unplug 02 sensor to see if it made any change, so I moved the plug (to unplug it) and the idle dropped down to about 800rpm. Been driving it around all weekend and its been perfect so i guess theres a loose connection somewhere