Where is the IAC valve on my 1992 Nissan NX

In My Humble Opinion
1

Where is the IAC valve on my 1992 Nissan NX 1600 (manual transmission), and do you have any advice re cleaning it; e.g., special tools, other components that I may have to deal with/disconnect, etc.

After searching online for hours, I’ve concluded that my problem is a dirty IAC valve causing an erratic idle (one day, idle okay; next day, lower rpm’s and stall when I stop). I found a youtube video demonstrating the process of cleaning the IACV but on a car different from mine. I’ve searched for forums and photos, but everything seems to be geared toward people who have some knowledge of car engines. I’ve seen photos, but I looked under the hood of my car today and couldn’t tell where it is. I’m pretty sure I can do the job, but any instructions I find online refer to other parts (e.g., it’s next to the manifold, part of the throttle housing), and that’s no help. If the IAC valve is part of the throttle, then please tell me how to identify the throttle and remove/repair the IAC valve. Please spell it out for me – a photo would be nice, but in lieu of a photo, a very plainly worded, graphic description (meaning, non-mechanic terms, if possible) for someone who is handy and likes a challenge, but is not familiar with the nomenclature of car mechanics.

2

By all accounts the pain in my stomach is my appendix. Looking though medical books, I can’t seem to locate it.
Can someone point it out to me? A picture would be nice, a detailed diagram would be better.
All the medical textbooks I read seem to be geared to medical students. They say it is next to the intestine, but don’t make it clear just where.
I mean come on, I have an exacto knife and a bottle of bourbon, what else do I need to remove this sucker?

Sycorax no offense, but if you can’t identify the IAC maybe you should consider taking your car to someone who can identify the IAC and properly diagnose your problem.
But hey what do I know, I have only been working on cars for 40+ years.

3

Nissan talks about an Idle Air Adjusting (IAA) unit that comprises a housing with an idle adjusting screw, an Auxiliary Air Control (AAC) valve, and a Fast Idle Control solenoid (FICD). The latter two components seem to be collectively called the Idle Air Control Valve (IACD), and each of them has a plunger that apparently can be pulled out (or will fall out), and presumably the plungers and the bores they fit into can be cleaned to eliminate carbon deposits which can cause sticking. The passages that connect to these items should also be checked for carbon build-up.

Looking at the engine, you’ll see the valve cover with four spark plug wires going into it, with one plug wire being close to the oil filler cap. Going rearward (toward the windshield), you’ll see the intake manifold, a big housing with four passages (runners) going to the rear. On the driver’s side of the intake manifold is the rubber air intake hose (maybe 4" diameter). On the opposite (passenger) side of the manifold is the IAA. The AAC wires are sky blue and white with green stripe, the FICD wires are yellow and yellow with black stripe.

The idle adjusting screw is set via a somewhat complicated procedure, and is then meant to be left alone – it’s not meant to be used for routine adjustment, as the system will self-adjust when working properly. My advice is to not mess with it.

If you’re lucky, cleaning the AAC and FICD will restore proper operation. If that doesn’t do it, those parts may need to be replaced, or the problem may lie elsewhere.

It’s also possible that carbon build-up in the throttle body is affecting the idle. Going back to the intake manifold, the throttle body is where the air intake hose connects. Remove that hose and you can see the throttle plate, which is operated by a cable (coming from the accelerator pedal) on the side of the throttle body. If the bore around the throttle plate has carbon (open the throttle with the linkage piece the cable attaches to to see), cleaning is called for.

These items can be cleaned with spray carburetor cleaner, or perhaps better with throttle body cleaner. A toothbrush and some rags are the tools I’d recommend. BE VERY CAREFUL NOT TO LET A LOT OF LIQUID GO INTO THE INTAKE MANIFOLD. If too much liquid (and it doesn’t take much) gets into a cylinder it can cause hydrostatic lock when the engine is cranked, which could result in a bent piston rod = engine overhaul = very expensive repair.

What Rick said is not bad advice. Here’s the thing – it’s not that hard to do this, and it may well fall into your capabilities. BUT – it’s also not that hard to screw something up, and we have a lot of long-standing assumptions about what people know to where it’s hard for us to anticipate every possible mistake someone might make. If you can arrange for someone who is familiar with these systems to assist you, that might be very helpful.

4

Rick: I’d be happy to remove that appendix for ya – it’s a simple operation and I’d even give you anesthesia because otherwise you’d scream like a banshee from the very small incision required. I was offended that you were offended by a straightforward request for information that might save me some money. From what I read online, it seemed simple, but I am smart enough to know what I don’t know and what my limitations are. A simple “take it to a mechanic” (without the snark) would have sufficed.

Gary: Thank you for your informative (and polite) reply; I realized from reading it that I couldn’t handle such a repair, and I took it to my mechanic today.

5

What’s the matter Ricky – you don’t have a snappy comeback for this no-nothing, upstart woman who dares to wander into male territory? Update: my car is running fine now; I’m happy, my mechanic is happy, and it cost under $100. My advice: when someone posts asking for info/help with an auto problem, try to help instead of posting a snotty reply.