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Still Nissaning
825 Posts
Discussion Starter · #1 · (Edited)
This is the info that I posted over on
I don't want this info to get lost so I will post it here too.

EGR Valve and EGR system.

#1 Incoming Vacuum supply Line for the BPT (Back Pressure Transducer) and EGR.
#2 Outlet vacuum Line from the BPT to the EGR inlet
#3 Exhaust pressure sense line, which hooks from the bottom of the BPT to EGR
#4 BPT valve (Back Pressure Transducer)
#5 EGR valve (Exhaust Gas Recirculation)

How to test the BPT vlave.
With the engine off
In the first picture above unhook the incoming vacuum supply line (#1), and hook a hand vacuum pump to the BPT inlet.
Unhook the outlet vacuum line (#2) and monitor for vacuum. There should not be any vacuum leaking through while the engine is not running.
Next, unhook the exhaust pressure sense line (3) and blow into the line going into the bottom of the BPT. Vacuum should now be present at the outlet vacuum (#2).

How to test the EGR Valve.
First you do the flow test, when engine is warm and idling put your fingers under the EGR and push up on the diaphragm the engine should stumble hard or die.
Next, feel if it moves freely up and down with out any rough spots.
Rev the engine up to 4,000 RPM and let it return to idle, with one hand monitoring the diaphragm, it should go up , then back down and stay stationary at idle.
Lastly to test if it is sealing properly you will need to let the engine cool off, and remove the EGR valve.

Blow on the threaded port that hooked to the exhaust line (#2) Be sure to plug the hose that was hooked to the BPT (#3) before doing this.
There should be no air leaking through the valve.
Next pull up on the diaphragm (#1) while blowing on the inlet and plugging the BPT feed line.
There should be flow through the EGR.
Let off of the diaphragm and the flow should stop.

How to test the EGR control Solenoid.

(A) EGR control Solenoid
(B) Vacuum outlet line that runs to the BPT and EGR
(C) Vacuum supply line that comes from intake manifold.
(D) 2 electrical wires that run to a wiring harness connector.
There also is another vacuum line that runs from the back of this solenoid to the carbon canister.
With engine at idle, unhook electrical plug at the end of (D) and verify voltage of 12VDC on engine harness side between the two wires.
Now check for vacuum on outlet port (B) of EGR solenoid. A vacuum should be present (with electrical plug disconnected).
Next supply 12VDC to the EGR control solenoid, hooking + to white wire, and - to black wire (the connector should be marked with +/-).
The EGR control solenoid should close, and vacuum should be cut off from port (B).

If everything was in accordance from the above steps, then your EGR system is ok

FICD, AAC, and Idle Up Solenoids

The AAC (Auxiliary Air Control) solenoid is there to regulate/adjust the idle Air/Fuel mixture.
If it isn't working properly, or is gummed up, your engine won't idle smoothly and tend to die when warm.
The FICD (Fast Idle Control Device) is used to adjust air/fuel mixture and stabilize the fast idle when the engine is on the fast idle circuit
The Idle Up solenoid activates when there is a load on your engine at idle. Such as AC, power steering, or the cooling fan kicks on (alternator).

The AAC (Auxiliary Air Control)

The AAC (Auxiliary Air Control) Solenoid can be removed by taking out the two Phillips screws, and unplugging the electrical connector.
Be careful not to lose the small spring behind the piston when removing the AAC!

The AAC piston, spring, aluminum tube, and rubber gasket will need to be cleaned with carburetor cleaner to remove any gum or deposits.

Reinstall the AAC, and start the engine. Apply +12VDC to one of the contacts on the electrical connector and hook the other contact to ground.
You should hear a 'click'. The idle speed should change noticeably.

The FICD (Fast Idle Control Device)

The FICD is threaded into the back of the throttle body, and is difficult to get at.

The picture above was taken with the intake manifold removed from the engine.
Using a 19mm (3/4") crows foot or equivalent tool unscrew the FICD from the Throttle Body.
Take caution not to loose the spring or piston behind this solenoid!

You will notice that the FICD and Idle Up Solenoids share a common connector.
I would recommend cleaning the Idle Up solenoid also before re-installing the FICD

Clean the piston and spring with carburetor cleaner, then re-install.

When the FICD is installed apply +12VDC to one lead of the FICD, and ground the other.
Make sure you get the right two wires for the FICD, there should be audible click (engine not running)

Idle Up solenoid
Common symptoms of a dirty Idle Up Solenoid are engine dies at idle when AC is turned on, or when power steering is used.
The removal of the Idle Up solenoid is more difficult to do than the FICD, but can be done with a crows foot, or bent/cut 19mm wrench (3/4")
Be careful to not loose the spring or piston from behind the Idle UP solenoid!
The cleaning process is the same as it was for the FICD, and it has similar piston and spring behind it, so don't mix up which piston went to which solenoid!

Re-install the Idle Up solenoid, and apply +12VDC to one of the contacts and ground the other. Be sure you have the right wires.
You should hear an audible click (engine not running)

The Anti-Backfire valve (ABV).
The purpose of the ABV is to divert the air intake from the TBI when vacuum gets too high, such as when you suddenly let off the throttle at high RPMs.

This one is easy to test, simply remove the air filter housing (upper and lower), and start the engine. Rev it up to 4,000 RPM, and let off.
The ABV should open and intake vacuum should be present at the hose that hooked to the bottom of the air box. (While at high revs)

The ABV can also be removed for testing.

Blow into inlet hose (#1 above) , and no air should leak through to #2 hose.
Then hook a hand vacuum pump to the small vacuum line (#3 above) and the valve should open letting air through freely from #1 to #2 ports.

Still Nissaning
825 Posts
Discussion Starter · #2 ·
The Air Induction Valve (AIV)
The AIV is similar to an air injection/smog pump system.
Pulses from the exhaust are used to suck excess clean air into the exhaust manifold to help complete the combustion of unburned fuel, thus lowering emissions.

#1 Vacuum port from the AIV control solenoid
#2 Inlet air supply from the air filter to the AIV
#3 Outlet of the AIV that hooks to the big stainless line that runs to the exhaust manifold.

How to test the AIV.
With the engine off
Unhook the air inlet hose from the air cleaner housing (#2 ).
Blow and suck on the port, there should be no air flow at this time either way. Next, hook a hand vacuum pump to the vacuum port of the AIV (#1 ).
With vacuum on the port blow into hose #2, there should now be flow.
Then, suck on the same hose, there should now not be any flow.

How to test the AIV control solenoid.

A AIV control Solenoid
B Vacuum supply line to the AIV
C Vacuum supply for the AIV Solenoid
D The electrical wires that are plugged into the engine wiring harness.
There also is another vacuum line that runs from the back of the AIV control solenoid to the throttle body vacuum(E)

Unplug the AIV control solenoid electrical wires(D), and all vacuum hoses hooked to it.
Blow into the vacuum supply port (B), and air should flow out port (E), not port (C). Next, energize the solenoid by hooking +12VDC to the white wire and ground the black wire on the end of electrical wires(D)
Now, blow into port (B). Air should flow out port (C) and not port (E).

1 Posts
But where'd the photos go :(

Is there any way to recover the photos from this documentation? It's great stuff and I could really use 'em. If they're lost in the abyss I'll try to duplicate it once I can figure this mess out!


NF Mod/Nissan Master Tech
2006 Pathfinder LE, 2003 Frontier SVE
10,670 Posts
Is there any way to recover the photos from this documentation? It's great stuff and I could really use 'em. If they're lost in the abyss I'll try to duplicate it once I can figure this mess out!

Well, the post was 5 years ago... I would recommend you send a PM to bob89sentra to see if he still has the pics.
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