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Old 03-03-2013, 09:17 PM   #1
Tally HB
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Default Replacing the Wax-Type Fast Idle Solenoid (Z24i engine)

If you are having idle issues, too high idle that won't come down, won't idle at all when cold, then you may have to replace this stupid little solenoid on your throttle body.

It is the fast idle solenoid and uses a special thermo wax, to expand and contract, and rolls the fast idle cam with temperature changes.

It's not too bad to do yourself but there are some cautions and I hope to help out here with the replacement.

I do not know how similar this is on other Nissan 4cyl and 6cyl engines so use it as a guide only.


Part needed:

Airtex part number on box photo below:






Once opened the part will be inside along with this instruction sheet written in Chinese and very poor use of English:





This is the part you are replacing as it looks when attached to throttle body. There are two pieces in the box. The solenoid itself and the housing with water nipples. The solenoid fits into the housing and is sealed with an o-ring.





Tools Needed:

- Whatever you need to remove your air cleaner filter housing
- #2 Phillips tip screwdriver (make sure it has a good tip)
- Small flat tip screwdriver
- Maybe a set of pliers



Solenoid Removal Procedure:


Bring engine up to normal operating temperature then shut down engine

Remove your air cleaner housing

Remove the coolant hoses that attach to the solenoid (coolant will spill and it will be hot)

Remove the three larger screws that hold the solenoid to the throttle body. In the photo below, one screw is hidden behind the black coolant hose.

Remove the one smaller screw that holds the fast idle cam retainer bracket arm (this screw is small and easy to lose!)

Once the screws are removed simply remove the old solenoid from the throttle body.

Do so slowly as the fast idle cam is under tension and will spring around once the solenoid is removed.

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Old 03-03-2013, 09:18 PM   #2
Tally HB
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Default

Now let's look at this stupid little solenoid instruction sheet.

You have this thing in your hand and it is surrounded by a piece of metal and held in this fixture with a humongous coil spring.


Getting this out of this fixture was the hardest part of all of this install.


DO NOT REMOVE FROM FIXTURE UNTIL YOU ARE ABSOLUTELY READY TO INSTALL IT BACK TO THE THROTTLE BODY!!







Once you remove it from the fixture it will slowly start to expand. You need to get your retainer bracket on the solenoid and install it on the throttle body within ten seconds (according to the instructions). I was not successful in the ten seconds thing but it still worked just fine. Just get it on as fast as you can.

You have to hold the retainer bracket to the solenoid, hold the fast idle cam up and back against its spring pressure and put the solenoid assembly into place all at once. Put a couple screws in it and take a break.


Here is a photo of the retainer bracket:

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Old 03-03-2013, 09:19 PM   #3
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Once installed it has to be adjusted. Lets look at that procedure.

First, lets understand how this fast idle system works.


The throttle shaft on the throttle body opens the air intake butterfly within the throttle body. This lets air pass through the intake and increases RPM's. Just like a carburetor.

On cold starts with cold weather temps outside, you need more opening to increase the idle until the engine is warmed up a bit. On these earlier computer controlled systems they use a solenoid of some kind to up the idle.

This particular system uses a spring loaded fast idle cam and this here solenoid to allow the fast idle to raise the idle up.

On cold start, the wax unit allows the fast idle cam spring to "roll" itself clockwise. As it rolls clockwise it pushes the throttle linkage open farther than at regular idle. This gives you a fast idle for the cold start. As the engine heats up, the wax solenoid pushes the fast idle cam back off fast idle and holds it there as long as hot coolant is circulating through the solenoid body.

Below you can see the fast idle cam and the throttle roller and understand how, as it rolls the cam over, it pushes down on the throttle roller and opens the throttle butterfly farther:

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Old 03-03-2013, 09:20 PM   #4
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To adjust this solenoid the engine has to be at hot operating temp (normal).

Look at the face of the fast idle cam and you will (or should) see the tick marks. You may have to clean yours off with a brush and carb cleaner to see them.

At hot idle the tick mark labeled "A" has to be centered on the roller pin.

This photo again shows the marks:









If, once installed, the marks do not line up you need to make an adjustment.
To make this adjustment, unlock the jam nut and turn the cam alignment screw in to move the mark left or turn the screw out to move the mark right. Once adjusted lock the jam nut.


Last edited by Tally HB; 03-03-2013 at 09:25 PM.
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Old 03-03-2013, 09:20 PM   #5
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You can also adjust the position of the throttle roller. You may have to do so to get proper alignment of the mark and the roller. This also adjusts idle speed.


Turn the screw marked S2:

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Old 03-03-2013, 09:21 PM   #6
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Once these two adjustments are made you should be good. But, if needed, you can still set base idle with the idle adjustment screw. This sets minimum idle position and controls the movement of the entire throttle shaft.

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Old 03-03-2013, 09:22 PM   #7
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I hope this helps someone out if they need to install one of these solenoids. It is common for them to go bad and cause idle issues.

Still, there are many other things that will cause high or poor idle.

You also need to diligently check for vacuum leaks. Any old cracked vacuum hoses anywhere on or around the engine will cause erratic, high or stumbling idle.

You can take a pair of needle nose pliers and pinch all hoses, one at a time, and find a leak. Pinching the hose causes the vacuum suction to stop. If you find one that changes the idle replace it with new flexible vacuum hose immediately.
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Old 08-21-2014, 08:23 PM   #8
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where you order the new solenoid
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Old 08-21-2014, 08:30 PM   #9
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Search google for the part number on the box
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Old 05-29-2016, 03:29 PM   #10
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is this the same one for the 87 v6 trucks?
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