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How To Service your VQ35 Fuel System

September 17, 2013

Today we are looking at the VQ35, Nissan’s stout V6 that eventually led to the return of the Nissan to racing prominence and also the Skyline here to the States. While this motor can be found in many different vehicles, often times we are asked where the FPR is located on the VQ because of the OBDII Error Codes P0171, P0172, P0174 and P0175.

These codes are related to the How To Service your VQ35 Fuel System and are reported for overly lean conditions as dictated by your PCM. If you are here to learn How To Service your VQ35 Fuel System, this article is for you.

P0171 Fuel System Lean, Bank 1
P0172 Fuel System Rich, Bank 1
P0174 Fuel System Lean, Bank 2
P0175 Fuel System Rich, Bank 2

First off find a flat level surface for you to work on, and also a friend who can keep an eye out for leaks, smells or any potential spills. Whenever you are dealing with fuel, your fuel system and related components keep safety first and foremost in your mind. Stay in a well ventilated system and do not smoke around or near the vehicle when you have your fuel lines open.

This guide is for educational purposes only, if you are not comfortable working on your vehicle take it to an experienced mechanic or a ASE certified shop to proceed. This article on How To Service your VQ35 Fuel System can be dangerous, and if you are not sure of what you are doing, please stop.

First relieve the fuel pressure in your system by undoing the fuel pump fuse located in your engine bay and starting the motor until it stalls out. After your vehicle stalls out, try cranking the motor over again to ensure the lines are empty. Disconnect the negative terminal on your battery to prevent any sparking.

Now with the fuel pressure released in your system, you are ready to begin. Disconnect your engine cover by undoing the 10mm bolts and nuts that hold the plastic to the top of the intake manifold. Unplug your MAF and disconnect your intake snorkel and intake boxes that lead up to your throttle body

With the intake removed, you are now ready to crack open your intake manifold. Disconnect your throttle body and all the related sensors like your Intake Air Temperature sensor. We like to undo the manifold by reversing the torque down sequence on the intake manifold bolts

With your upper manifold undone you can move ahead and remove the lower plenum to expose your fuel injector rails and the fuel pressure regulator.

Before undoing the fuel injector rail, make sure to disconnect the fuel feed quick connect located under the intake manifold base.

Undo the fuel injector rail and lift up on the entire assembly. It is not shown here, but DO NOT DROP anything into the lower runners heading into your head. Use tape or rags to stuff the openings closed here.

Here is a blown up display of the regulator that is connected to the fuel injector rail itself. Remember your vehicle is not equipped with a return line stock and thus your regulator is located on the fuel injector rail feed.

Your replacement part from Infiniti / Nissan is 22670-8H300.

Make sure to mount this unit cleanly and without any damage or debris that may cling or prevent the oring on this intermotor regulator to become clogged or leak. Assemble your intake manifold and fuel injector rail in reverse fashion, do not forget to use the torquing sequence for your intake manifold.

Once the vehicle is back together, make sure to start it and check for any leaks near the lower intake manifold plenum and valve covers.

Now your lean condition should be taken care of and you now know how to service your VQ35 fuel system, clear your OBDII codes and you are ready to rock and roll!

Happy Driving!