See page 2 for pictures of my car

2nd Generation Maxima Air Regulator Repair

If your Maxima stalls and is hard to keep running on cold starts, you may have a bad air regulator. It is a very common problem on the 2nd generation cars and also on some early 300ZX's I'm told. A new regulator is around $100 from the dealer, but this fix will cost less than $1 and is very effective. Read on.

This may sound complicated, but it really only involves drilling and tapping one hole. It's not as bad as it sounds. I'm giving you an explanation of what's in the valve, so you'll have a better understanding of why your valve doesn't work anymore. But you really don't need to know any of that to fix your valve.

The valve is located on the back of the intake plenum above the rear valve cover and just below the hose between the PCV valve and the rear valve cover. It is held in place by two 10mm screws and has a wiring connector for the integral heater as well as a hose attached to it. There�s an o-ring between the valve and intake. Don�t lose it if you remove the valve. I scanned my '87 Maxima service manual with a locator picture and a picture and description of the valve.

Even though this apparently is a very common problem on these cars, you may want to check a couple of things to make sure the valve is indeed bad before doing this mod. Refer to Figure 3. You should check to make sure you have power to the integral heater element and also check the coil in the heater with an ohmmeter for continuity. It should read approx. 70 - 75 ohms between the two terminals on the regulator, and you should have battery voltage with the ignition on at terminal B of the wiring harness plug. If the heater doesn�t work because the element is open, it would probably take a long time for the bimetallic element to warm up from radiant heat off the engine and allow the shutter to rotate and close off the port, allowing the idle to return to normal. If the element is bad on your valve, you may want to go to the junkyard and get a valve with a good heater element in it to modify.

The next picture shows the valve housing cut open so you can see the shutter plate mechanism. The end of the bimetallic element is under the gold colored round cover just above the pivot point of the shutter plate. The "P" shaped cutout in the shutter plate (below the center pivot point and to the left of the spring) is covering the port opening, which should be slightly exposed when cold. When the valve ages and the element loosens slightly as this one had, it doesn't open like it should when it cools. You're going to put a screw in the housing to help open it slightly when cold, but it will still be able to close when it warms up.

It will probably be easier to do this with the valve removed from the engine, because you will be able to look in the hose nipple and see when you've adjusted the screw properly, but I suppose it could be done on the engine if you're careful. You will need to drill a .159" (#21 drill to be exact, but a 5/32� should work if you don�t have a #21) hole in the neck of the valve as shown in the next picture.

There is a phillips head screw installed in the hole in the picture. That's what you're going to put in it after it's drilled and tapped. You will notice that there are two holes drilled in the neck in this picture. This was my prototype and I was experimenting with the location. You will only drill one in yours. The location of the hole you're going to drill should be 1.75" from the split line between the black plastic wiring socket and the metal part of the valve. The hole should be as close as possible to parallel to the blades of the electrical socket in the end of the valve. This positions the screw to push perpendicularly on the bimetallic element when you adjust it. See below for an end view showing the orientation of the screw.

You will also notice a drilled spot near the top on the flat part of the valve body above the nut which holds the shutter assembly in place. This was where I drilled trying to disassemble the valve. Don't drill anything there on yours, and don't mess with the nut either - it hold the shutter assembly in place and should have some type of sealer on it (which I removed during disassembly). You don't need to loosen the nut to do this mod.

After you drill the hole, tap it for a 10-32 screw. Install a screw approximately �� - 1" long. You should also put a 10-32 nut on the screw before you install it and screw it all the way on, just under the head of the screw. This will be your lock nut after you adjust the screw. Turn the screw in gently until you feel it touch something. As you screw it in further from there, you're pushing on the bimetallic element and rotating the shutter plate to open the port. If the valve is removed, you can see this by looking in the hose nipple on the valve and see the shutter opening the port. Start off with a small amount of opening; say 1/16" - 1/8". It doesn't take much. Reinstall the valve, but don't forget the o-ring seal. Then start your engine and the cold idle should be faster. You can play with the adjustment of the screw to raise or lower the cold (fast) idle to suit your liking. Once you get the screw where you want it, hold it in position while you tighten the locknut against the valve body. Don't over tighten it or you�ll strip out the hole. The valve is made of pot metal, and it's a little on the soft side. You only need to gently snug it down. Once your adjustment is complete, you should put some Loctite on it or a small dab of RTV to prevent it from loosening.

The idle speed should drop down to normal within a couple of minutes once the engine and regulator valve warm up. If the idle speed stays too fast after the engine is warm, you may have the screw adjusted just a hair too much. What I did was wait till the engine was fully warmed up, and then adjusted the screw on the regulator till the warm idle was where it was before I did the mod. Then, after it cooled down completely, the cold idle was still fast enough. It may take a little tweaking to find the balance between cold startability and warm idle speed.

If you have any questions or problems doing this mod, sign my guestbook or drop me a note at pkfinn@bellsouth.net. I�d like to hear how it works for you.