HIGH IDLE AHHHHHHHH!!!!!!!!!!!!!!!

[300freekzx]

I noticed that my IAAV does nothing to stop the high and erratic idle of my z I turned the idle screw all the up and down with the connector disconnected and she just sat there at 1500rpm. As matter of fact, the connector has a broken wire so it is not really connected anyway. I need help b/c this shiit is driving me crazy. Also if anyone have a clear diagram of the vacuum set up on an N/A motor may I please have it. I am willing to pay also. At least is there anyone in the Columbia, SC with a z32 that I can look at to make sure my vacuum lines properly connected. Thanks!

[Zwicked]

If you adjust the screw on the IACV unit where the AAC solenoid and nothing happens, you have some other issue as well, my guess is either:- a vacuum leak- Aux. Air Valve stuck open

Fix the wire on your AAC regardless and test the AAC to see if it works.

Vacuum diagram in manual:

http://www.300zx-twinturbo.com/cgi-bin/manual.cgi

Start at chapter Engine Fuel and Emissions Control System, page 11 and forward shows it all

[300freekzx]

Thanks.

[300freekzx]

I checked all 14 vacuum lines and all are fine. I have to reconnect that AAC wire. So I will check the AAV to see if it is stuck open. How exactly does one do that? Thanks for being understanding of my Z ignornace.

[Zwicked]

Test the AAC solenoid before you reconnect the wire. Run a 12 volt +/- wires to it and touch the 2 terminals momentarily. You should be able to hear the solenoid click. If not it might be dead. The ECU is rapidly and constantly modulating the AAC, so it is a very important item to have working correctly.If it's ok, then set the idle with engine warm to about 600 RMP and then plug the connector back onto the solenoid. It should immediately raise the idle to about 650~700. At that point you will know the AAC is doing it's job.

For the AAV, you need to take it off, but try testing it first.Take a pair of long nose pliers or vise-grips. Clamp the hose off that's on one side or the other of the AAV. If your idle goes back to normal, you've found the problem.

Luckily there are only 2 easy to get to bolts (relatively speaking!) and no gasket or anything as it is just secured to the plenum. Once it's off, look into the hole where the hose connects. You should be able to see a crescent shaped hole through the other side. Connect 12 volts +/- to the 2 terminals and let it sit for a few minutes. That disc should have now closed and you should not be able to see through it. This is what lets extra air in for raising the idle, and closes off to return it to normal idle.If it doesn't seem to work take it apart and see if it's clogged/seized with oil. If it's not, it likely means the bi-metal spring is cooked. I have a few extra of these, so if yours is bad you can have one if you pay the shipping from Canada.

Just one question: I assume you have checked your throttle and cruise cables etc to ensure the throttle bodies are fully closing?

Modified by Zwicked at 9:38 AM 1/31/2008
Modified by Zwicked at 9:39 AM 1/31/2008

[300freekzx]

Yes I have checked the throttle body. They are closing but It will never hurt to look again. I will run the test sunday as that will be my next free day. I have an extra AAV from my old motor. It worked fine before the motor croaked I will try it. I will have an update soon. Maybe I will get to do it in the morning if I am not as sick as I am now.

[300freekzx]

Okay I did the clamp test to the air regulator and it nothing just sat at 1500 rpm. However, when fist cranked the car up tonight she idles down to 1000rpm and sat there until I gave her a little gas. Then she when back to 1500 then to 1800rpm then back to 1500rpm. I will perform the other test on sunday.

[zin999]

disconnect the throttle cable and cruise control takes 20sec and start the car and see where it idles.

[300freekzx]

Just wondering but why my friend????

[300freekzx]

here we go. I reconnected the wires to the connector for idle air adjustment valve and no change. correct me but when I adjust the idle do I take off the connector that is blue or the one that is black to adjust idle. I also notice that there is a shortage somewhere in the big tube of wiring in the back next the fire wall. When I move the idle drops down then when I move it again it kicks back up. Whats up with that I also notice I have fuel leak from the line to the damper.

[Zwicked]

OK, if you di dht eplier test then the AAV is ok.

To set the base idle you unplug the AAC. That's the upper round shaped solenoid on that casting, not the lower hexagon shaped one. The lower one raises the idle when AC etc and other loads are on to compensate.After you unplug it, adjust the idle screw on the side until it's at about 600 RPM, and then plug the AAC back in. It should raise the idle to about 650 to 700.

I would do this first if you haven't already just to rule that out. The connector is clean etc?

You probably need to troubleshoot that wiring condition as well though until you find out which wire is doing that.

[300freekzx]

Great well I will try that in the morning.

[300freekzx]

I tried all test even disonnected the cables for the throttle body and no change in idle. I have noticed a foul oder coming from the exhaust I wonder are my cats bad. Do you think that there might a problem there as to why she idling high.

[Zwicked]

Question: did you fix that wiring that you said altered the idle speed when you were moving the harness at the firewall?

Generally speaking if the car has fuel and spark, it's only the amount of air that can increase the idle. That would come from a hose off or leaking, throttles open, or idle control set wrong.You mention you turned the idle screw on the side of the IACV body, so it's not that. The AAV seems to be working as when you pinched the hose off, no change.Also you mention you disconnected the throttle and ASCD cables so the throttles are not being held open by themSo, there has to be some other way air is getting in unless someone messed with the screw at the throttle bodies that syncs them and adjusts base stop for the closed position. You could pull the hoses just to see if the flaps are closed .I know you said you checked all the vacuum hoses for correct locations, but I am leaning towards a leak somewhere.Troubleshooting from a distance is far from an exact science unless the issue is obvious.I would probably next perform a leak test by installing an adapter in where the air filter connects and pressurize the system with a 3 or 4 pounds of air and see if it leaks down real fast and find it by listening for the leak to track it down.

***Has there been any other work done just before this issue arose, like the plenum off or FICD casting taken off the plenum or something?

***Does the engine run perfectly other than hi-idle?
Modified by Zwicked at 2:19 PM 2/4/2008

[300freekzx]

I fixed the wire. I will pull the air ducts off in the morning and make sure the throttle bodies are fully closed. I checked the TPS before and it was in spec. with throttles open and closed. The guy who installed the motor could have messed with the throttle screw. As a matter of fact they were tampering with it when I got the car back. I will check and give an update. Hey man thanks for everything thus far.

[Zwicked]

a bad TPS won't cause hi-idle, but good to check anyway.

The FSM tells you how to set TB's up correctly.

http://www.300zx-twinturbo.com/cgi-bin/manual.cgi

Engine Mechanical starting on page 23
Modified by Zwicked at 9:10 AM 2/5/2008

[300freekzx]

Checked those and everything is in spec. I may have to break down and go to stealership

[Zwicked]

That would likely be a big mistake. Is there any forum member near you that might lend a hand? Most dealership mechanics, aside from a few, have never worked on a Z or it's been so long they forgot.Especially when it comes it your type of issue and throw a motor swap in for good measure.My wife insisted on taking her 240 in and they spent lots of my money and never found the bad idle. After she was satisfied and I was broker, I looked it over and 2 hours later it was fixed.

Did you do the pressurized leak test as I mentioned? That always confirms if it's getting air where it's not supposed to.

[300freekzx]

You have a very good point. That is why we call them the stealership. No there is no one here from this forum that I know of. Can you give me details and the pressure test as I never done this. Once again thanks man.

[Zwicked]

Sure.

- You need an air compressor with a reasonable size tank as the engine holds a fair bit of air and some will leak off-Go to Home Depot or any building supplies store. Purchase a 3" PVC plumbing plug-Pick up an airline male quick connect fitting with male threads-Grind or sand the threads off the pipe plug so it's smooth-Drill a hole in the end of the plug and thread the air line fitting inDONE!

Remove your air filter/MAS and insert this plug, tighten the clamp.

Connect air hose with gauge and shutoff valve and charge the system.

BE CAREFUL...you only want maybe 3 or 4 pounds of pressure as your entire engine including seals will see this. It's important you have a good gauge on the line so you can keep the pressure low and accurate.

If you do this in a quiet area you will be able to hear any leaks. A 3' piece of hose and your ear works well to locate them.

When you pressure it up and close the valve, if it's as close to perfect as needed, it should hold air and slowly bleed off in 15 seconds or so as some inevitably leaks by but if it's tough to get it up to pressure or when you shut the valve it's down to zero immediately there are leaks.

Just keep the air on in this case at real low pressure and find the leaks and fix 'em.

AAC top pressed in piece or the many hoses are common. Not so common but possible are the plenum gasket if someone had it off and didn't install it right or FICD casting was off and same thing.

[300freekzx]

Great I will check it in a few days. I have new problem now. I drove the car for a little while and I got down on her a little and now she is running like not all injectors are firing. I think there is problem in the wiring harness. Will update soon. BTW is there a good tech guideon how to pull the wire harness to put new connectors on???

[Zwicked]

Before you go off and spend money on the wiring confirm that's what it is.

-Pull the CAS plug and see if it's corroded and clean it well and see if it's better after that.

-If not, pull the CAS off, turn ignition to on and rotate the CAS by hand slowly. You should be able to hear each injector click. Do this in a very quiet area, preferably indoors or you won't hear it.

This should confirm if the circuit is working. If it's not, now I'd pull all, or at least the one that doesn't click, injector connector and check for corrosion as well as test the injector to see if it's in spec. Using an ohm meter, it should read between 10 and 14 ohms.

*If you find one is corroded, chances are they are all like that and need cleaning.

[300freekzx]

thanks will do

[300freekzx]

Hey I went under the hood and it is definatly the injector connectors. When pushed down them the motor leveled off (sill ildes high) I will get some dielectric grease and clean the connectors. I will replace soon as they are in really bad shape. I am going to check the MAF also to see if it is dirty and in spec.

[Zwicked]

Right on! That's very often the case why these engines don't run right. It's too bad Nissan didn't choose a better plug.Hey, I'd recommend a set of small picks, files and a brass wire brush. It takes time, but clean as much visible contamination off as you can.I'd suggest finding and buying this cleaner if you can. It is the best for the money I have found as it cleans as well as enhances the connection. Also get some dielectric grease to protect them.

http://www.mgchemicals.com/products/801b.html

PS - use this on all the plugs (CAS, PTU, Coolant Temp Sensor, TPS, AAC, AAV etc)

[300freekzx]

I am going to do that over the weekend. I will replace those connectors soon b/c they are really crappy. My MAF is pretty dirty so I will clean that also.

[SpeedFreak_Josh]

While ur at it, remove the IAAV and soak it in top engine cleaner or fuel injector cleaner. Often times they have carbon buildup and stick. That may be the cause of your high idle problem. I've encountered this numerous times.

[300freekzx]

Ok I cleaned that MAF and I did not do the pressure test because I have another problem. I had a wire break on my injector connector and I got aggraveted and stopped working. I have all new connectors coming in. I cleaned the old ones and when I was putting them on one of the wires popped.

[300freekzx]

I await my connectors so I can get up and running once that is done I will be back to the high idle battle.

[300freekzx]

They should be here soon