When you’ve got an existing misfire condition in your Nissan or Infiniti 3.5 liter VQ35DE engine, it can be a huge problem and it doesn’t need to be. Today we’ll be covering how to fix VQ35 misfire in our comprehensive guide to resolving VQ misfire. From camshaft position sensors to ignition coil troubleshooting, if you’ve got a OBDII trouble code of P0300 or any associated misfire code, we’ll show you how to fix it.
The OBDII code of P0300 represents a serious misfire condition in your 3.5 liter Nissan V6. This condition can cause poor fuel economy and in extreme cases cause the vehicle to not start.
In order to use our How To Fix VQ35 misfire comprehensive guide, we’re assuming you’ve already pulled your OBDII trouble code from your Infiniti or Nissan.
The trouble code of P0300 can also be accompanied by other misfire codes, mostly cylinder specific. Because so many things go into your running VQ35DE engine, this can be caused from any number of problems with your engine. Our comprehensive guide has already assumed that you have checked :
Faulty catalytic converter – A fishy egg smell from your exhaust is a sure fire sign your catalytic converters in your VQ have failed. Replace these to resolve your P0300 trouble code.
Bad EGR valve – The EGR system has a leak or break in the tubes or hoses, or your EGR valve may be stuck or burned open / shut.
Bad Spark Plugs – Needless to say, if your spark plugs are in bad shape, nothing in this guide will be able to help you. Replace your spark plugs right away and clear your code to see if the P0300 returns.
How To Find the Misfiring Cylinder
Before we show you how to find the misfiring cylinder in your VQ35DE, you must first raise and secure the vehicle. Take the proper steps to ensure that the front of the vehicle is raised if you mean to check your crank position sensor. If you do not mean to test your crank position sensor in your VQ35, you can keep the vehicle on the ground.
To begin our How To Fix VQ35 Misfire DIY guide, you will need to remove your stock or factory air dam and funnel ram inlets. These are secured to the front hood bonnet by way of plastic clips. Remove the plastic shroud all together, and remove the factory air filter element. Unplug your mass air flow sensor, and you are now ready to remove the intake pipe.
Now undo the clamp that holds the intake snorkel and boot to the throttle body inlet. With this clamp removed, you’ve got to disconnect the big vacuum hose before removing the entire intake system. You can leave this open or shove a temporary bolt in it as you are testing your VQ35 to locate the misfiring cylinder.
Now remove your entire intake system up and out of your engine bay. You will be eliminating the huge air box section of your intake system, so that you can test your driver side coils without having the entire intake in the way.
Now remove this clamp that holds the first part of the intake elbow to your plastic intake box. Flip this clamp over and reverse it so that you can tighten and adjust without removing more than what you need to.
Head over to the driver side of the engine bay ( Bank 0 or Cylinder 1 side ) and remove the 10mm bolts that hold the engine harnesses and engine harness brackets in place.
Next up you’ll start by unplugging the engine harnesses shown below.
Repeat this process on the drivers side ( Bank 1 ) and unplug the very same harness. This step should be easy now that your entire intake is removed.
You can now cut the zip tie that holds the engine harness around your VQ35DE engine.
This is to make room so that you can access the ignition coil connectors, or simply disconnect the ignition coil all together.
Disconnect the PCV hose from your valve located on the passenger side of the VQ engine. This is a big part of testing the #1 cylinder for misfire, because you aren’t disconnecting anything with the PCV hose connected.
Remove all the 10mm bolts that hold your ignition coils in place, but leave the connectors.
The most problematic ignition coils you’ll be testing in this DIY How To Fix VQ35 Misfire Guide is this ignition coil shown below the fuel pressure damper, and the number 1 cylinder up front on the passenger side.
Now that you have all your ignition coils disconnected and freed up, go ahead and reconnect all the engine harnesses you unclipped before. Make sure you connect them but make sure that the engine harness is pushed up and out of the way.
You’ve reached the custom intake part of our How To Fix VQ35 Misfire Guide, and as we mentioned earlier, you are removing the hard plastic casing of your intake pipe. To remove this section, loosen the clamp that’s on the mass air flow sensor housing side.
Now you should be able to remove the air mass flow (MAF) sensor housing, and you’ll be shortening your intake by putting this onto your intake coupler. You may or may not have to remove your hood for this step depending on your mods and if you have any strut tower bars in place. Make sure to tighten the MAF to your throttle body inlet, and then pull the MAF engine connector up to connect to your mass air flow sensor.
When you are done, you should have something that looks like this in your engine bay. Don’t bother putting your air element back or any of the other plastics. Just make sure you’ve reconnected all the engine harnesses, and then start your car with it in PARK or NEUTRAL.
Now that your VQ35DE is running and your intake pipe is short and out of the way, you can begin locating the trouble cylinder by unplugging your coils or pulling up on the ignition coils.
Disconnect your ignition coils one at a time, until you locate the ignition coil that is the problem. If you disconnect an ignition coil and your engine idle or misfire does not change, chances are the ignition coil is bad. Learn how to test a VQ35DE ignition coil by checking our guide here, or you can simply choose to replace the ignition coil.
Q : What do I do if this How To Fix VQ35 Misfire DIY article does not locate my bad coil?’
A : Check your VQ35 camshaft position sensors to see if they are causing the problem. Click here for our How To.
Q : What if my coil shows bad, but checks out okay electronically?
A : Remove the boot to your VQ35 ignition coil to make sure there’s no breaks or corrosion on the contact spring.
How to Inspect VQ35 Ignition Coils
To inspect your ignition coil boot and interior contacts, simply take your VQ35 ignition boot and gently pry at the inlet.
The interior contacts must be clean and free of any debris or breaks. Potential misfire can occur if you flip this contact around, or there’s any cracking or distress to the spring or contact leads.
Once you’ve checked your ignition coils, go ahead and replace them to complete our How To Fix VQ35 Misfire guide. Have any questions about this article or how to check your VQ35 ignition coils or misfire problem? Comment below and let us know!