BushM4

I bought my daughter a 1990na and the idle is running 1000 rpm. I tried the throttle adjustment screw and it is all the way in. Out of course increases the idle. I squeezed the hose running from the balance tube to the IACV valve and the idle went down. So I have two questions.

Number one. To try and free the stuck valve do I just spray WD40 into the valve while the engine is running or off.

Number two. If the WD40 trick doesnt work, For a temporary fix till the new part comes in, can I reduce the ID of the hose to lower the idle. I would place a smaller hose inside of the factory hose to achieve the air flow reduction.

Thanks, Mike B

rtmorgan

mine has been running at 1000prm for a while (i have the same problem)

i have had no problems with it runnng that high. my a/c runs a little better at idle due to the higher rpm

Sweets

I would just let it idle at 1k until the new part comes in. It's not hurting anything.

KasbeKZ

yeah. let it sit at 1k.

these cars should almost never need the idle screw adjusted. once you get the new iacv on, you should go through the write up for properly setting the idle and never touch that screw again. the car compensates for idle by itself, so adjusting that screw just puts your automatic components closer to their maximum adjustment. a rough way of explaining it, but you get the point.

btw, something i lately have been wishing someone told me before i got a 1990: the '90 has 26mm rotors up front (off topic i know. it's good to know though) and they warped a lot more easily than all the later rotors. so if these rotors warp, don't get new '90 rotors, just get calipers from a later car and get the new rotors for a later year. brakes will be a lot better then. don't even bother turning these. they can't afford to be any thinner.

CanyonCarver

Any ecu codes, like for the coolant temp sensor?

I have a process by which I regularly clean my t/b's and IACV with carb cleaner and then spray in some WD-40 afterwards. No disassembly required. I'm pretty sure I posted a write-up here a coupla years ago. You might do a search.

BushM4

I need to clean the TB's. Gonna wait for a day in which she can help. She needs to learn. Im now a little confused because at another forum a member said that its the AAC valve not the IACV that the hose from the balance tube connects to. Now according to this diagram http://www.courtesyparts.com/300zx-z...8638_8646.html its the IACV that connects via the hose to the balance tube and the AAC connects to the IACV. I pinched off the hose coming from the balance tube to what the diagram says is the IACV and the idle dropped. So according to various forums and service manuals the IACV is stuck open or partially open or the electrical connection is bad. So Im going to clean everything before I order parts and I need to clarify if its the IACV or the AAC that is first in line off the balance tube hose.

KasbeKZ

those two are in line. they both do the same thing (allow more air in to raise the idle) pretty much. either one can be your problem, and either one can be cleaned just as easily. i would take all the hoses involved off and blast into both of them with wd-40 and see if that helps. i bet it will. it helped mine.

BushM4

Thanks. My daughter has prom tomorrow so Sunday early afternoon we are going to clean the TB and the valves in question. If it doesnt help, I'll block it off till I order whichever is bad.

KasbeKZ

i wouldn't block it off. really, just let it idle at 1k. no big deal. i idle at 1200 and still make 23 mpg, which is more than car and driver rated the car at. if you block it off, it won't run when you cold start it.

BushM4

Gonna clean the TB and those shoot those valves in question. If cleaning doesnt work then I'll restrict it (not a total blocking). When I squeezed the line I didnt have to close it shut to get the idle to drop. Just a temp fix. Its an automatic and she is a fairly new driver and it tends to lurch when putting into drive.

KasbeKZ

oh oh that changes it a little. i'm pretty sure cleaning them will help you out.

CanyonCarver

Cleaning should be the first task, then I assume that you've followed this procedure?

http://300zx-twinturbo.com/cgi-bin/m...ault&total=190

And procedure 40 & 41 here:

http://300zx-twinturbo.com/cgi-bin/m...ault&total=190

rtmorgan

how the **** you get 23mpg? i get 16-20

CanyonCarver

I've gotten as high as 27.3 mpg running across new mexico and texas at 80-90 mph.

KasbeKZ

yeah you might be running rich. do you have new 02 sensors?

BushM4

Update. I cleaned the TB's and cleaned all electrical connections (some where pretty bad) and tried the WD40 to get the high idle corrected. Didnt work. Ordered the part. Going to tackle the PCV's also when it comes in. Will keep you posted. Thanks again.

KasbeKZ

surprising.

BushM4

Got the regulator yesterday. Installed it today. Pain in the *** to get that bottom bolt. Anyway its running fine now. Thanks for all the help.