Vehicle is a 1984 300ZX Turbo 3.0L V6 manual. The engine idles too high. It idles at 1400 rpm and a MT turbo should idle at 750-800 rpm. Used FSM to perform diagnostic procedure and driveability test. Manually set the idle speed by adjusting the engine speed screw on the side of the A.A.C. Also made an adjustment to the throttle valve switch. That brought the idle down from 1800 rpm to 1400 rpm. ECU codes are normal. Besides the air regulator, not sure what else it could be. TxGreaseMonkey, I sure hope you're still around. You're the only one that seems to know anything about these cars. I will try to post a video tomorrow.

Check the Idle Air Control Valve (IACV)--it may need cleaning or replacing. Also, look for any air leaks; i.e., metered air downstream of the MAF Sensor. This includes making sure the PCV system operates properly. If you end up replacing the IACV, I would go OEM. I've had many problems with after market IACVs. Invariably, they end up causing the idle rpm being too high, upon startup, and taking a long time to step it down. When you start the engine, the throttle plate should be closed and air should be controlled by the IACV. If the PCV valve leaks, or there's an air leak in the PCV system, the air will be metered and allow the engine to idle way too fast.

The first thing I did was replaced the PCV valve and the hose. The PCV valve probably didn't need to be changed as the part was still good, but I did it anyway. It was cheap. I have also heard that drivers have had issues with non-OEM IACV's. I always buy OEM parts. :) Even though they are more money, it's worth every penny. I tested the continuity of the IACV with a multi-meter, and there is no electrical continuity. I think it's a safe bet that's the source of the problem. I will be replacing that part. I think I should also replace the harness to the IACV if I can find the part #. I was not sure which part # to order from Nissan.

If there's no voltage to the IACV, there could be a problem with the ECM. Disconnect the battery and clean the main ECM ground. While you are at it, be sure to clean all grounds. The reference voltage to the IACV should likely be around 5 volts. Be sure to test all under hood and under dash fuses with a test light or multi-meter.

I apologize for the late reply. The car has been being diagnosed at the shop. It's the Auxiliary Air Control (AAC) Valve. I believe it learns the idle of the car and operates at a specific target RPM for manual transmissions. The valve is stuck and I think the part is sealed so it can't be easily fixed. The part no. is 23781-01P07 and Nissan no longer makes the part. This limits me to searches on the forums and junkyards and that's kind of a crapshoot for parts.

They show aftermarket at carquest.

CARQUEST Auto Parts - Engine Controls Catalog - 0283

Yes, I checked similar auto part websites. They list them as available, then when you proceed to checkout they say they have a quantity of 0.

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Originally Posted by DanPatrick10

Yes, I checked similar auto part websites. They list them as available, then when you proceed to checkout they say they have a quantity of 0.

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I know you were looking for OEM. But that store is nationwide so it might not hurt to give them a call if one is located near you.


CARQUEST Auto Parts® - Great people, great products, great prices!

It didn't matter if it was OEM or aftermarket as long as it worked. I checked with Carquest which directs you to Advanced Auto Parts. I gave Advanced Auto Parts a call and they were unable to special order the part. However, my mechanic said he cleaned up the IAC and put new gaskets in from Nissan. That brought the idle down to 1100 rpm, so it's much better than it was before. We both thought it was funny how they still sell the gasket for the part, but not the whole part itself.