Cold idle issues

[mook]

Not sure if this is electrical or mechanical, so putting it here. Had a search on idle and adjusting and didn't really find a difinitive answer to the issue I have.

Basicly, when cold the idle is way too high, something close to 2000rpm. Then, when I reverse off the drive and dip the clutch to change into first it'll go upto 2300rpm, sometimes more. That can't be right!

Had a look at it this morning and have made some adjustments. There's a little piston underneath the throttle butterfly switch which looks to adjust the throttle stop position. Having cold started it and shoved it this way and that I've adjusted the idle screw on that so it sits lower and doesn't hold the butterfly open so much. Then also adjusted the normal idle screw out a little as warm idle was around 1200rpm. Have got warm idle down to 1000 but it's obviously still a little high and I can't really see where to adjust it further (there is more room on the idle screw but the butterfly doesn't quite reach it now, even when warm - possibly need to adjust the cold idle bit again) I've given the piston mechanism and surrounding area a spray over with GT85 incase it's a bit sticky.

Anyway, just wondering if anyone knew a 'oh yes, it's this' for this one. I've cleaned out the butterfly as it was a bit gummed up but have not yet removed and cleaned the idle control valve, or anything on the AFM. Guidance appreciated :thumbs:

 

[Matt_S]

Check the manual. The 'piston' is a wax pot type potentiometer thingy. (See, Im way too technical sometimes!)
As it heats up it retracts with the pressure of the spring. You need to set this up as per the manual. We did it a few years back on my mates car when we fitted a different throttle body. I wouldnt go messign too much without consulting the manual. Its a bit 'round the houses' and long winded sometimes, but its best to be safe than sorry.

You could try removing the AIC and AAC body - the little assembly that sits on the engien side of the plenum. THis controls the air that goes into the engine when the throttle is shut once fully warm. This is supllemented with the additional air that the slightly open throttle body gives when in cold start woith the 'wax pot piston' operating

 

[Ozone]

I have to same problem with mine. Previous owner took it to the Nissan dealer and they found nothing wrong.
Mentioned it to my mate with an S14, his car does the same thing and always has!
How bad is it?
On mine it only idles high for maybe the first 30 seconds on a cold day (2000~2300rpm) before it settles (to around 1600rpm, slowly reducing as the engine gets warm).

 

[mook]

Well, it seems to have settled a little now after my fettling. Cold start is only around 1500 rpm and it comes down more quickly than it did before, without much of a rise after first moving off. More managable now

 

[jhinchy]

My one idles quite high when started from cold, i assumed it was something to do with the PowerFC not being as advanced as the original ECU for the more mundane jobs.

 

[slammedmind]

mine does the same, my tuner rekons its the afm most of the time but normal.