Nissan Repair Questions? Ask a Mechanic for Answers ASAP
Hi, My name is*****'m happy to help you. During our conversation, I may be presenting you with different things to try, and ask you some Questions to get a better understand of the issue so I can answer your question properly. So stick with me to the end, and I am sure we should be able to get this issue resolved for you!
There is a number of things that can cause a misfire. So I am going to need to pick your brain a bit to get a general idea of your car so I can offer some suggestions or things to check.
First can you tell me how many miles you have on the car and if you have any Mods? If you do have Mods, please list them.
Ok.. Thank you for that information. I am going to start with your K&N air filter. It is a myth on these cars on how they work. This is something I run into all the time. K&N air filters cause a air vortex in the air intake system which would typically be the best way to have air enter the intake system. But not for cars with the MAF sensor right after the air filter air box. The MAF sensors are designed to read air directly. When you cause the vortex the MAF sensor can not meter the air properly and will cause the car to run lean.
I had a customer with a 2007 G35 Sedan with duel intakes and had two K&N air filters and was dealing with a stalling issue. When I tried to explain to him the first step is to remove the air filters and then re-addapt the self learning he looked at me and cursed me out saying I did not know what I was talking about and left the dealer ship. On his way home, he had to prove to me that the filters were not the issue and stopped at a Nissan dealer to pick up a set of air filters. So he took out the K&N's and put the factory filters in. After a week of no stalling he actually called the dealership and asked to speak with me and apologized for his actions and told me what he did and could not believe how simply air filters can cause this.
So like that customer, I will ask you to start with getting a factory air filter. The second thing I am going to ask you. I am sure you changed the spark plugs. What brand spark plugs did you install?
Did you happen to find any oil in any of the spark plug galleys when you did the plugs? Some times oil can seep from the valve cover o-ring into the spark plug galley and cause misfire codes also.
When you change to the paper type air filter, I recommend the dealers filter. The quality is much better, and does not weather as do after market filters. So try that if you would
That is a picture I took to show the difference in air filter quality.
So do you recall seeing any oil in the spark plug tube? Cylinders 5 & 6 are the most common.
I have seen after market coils cause issues. But I would start with one thing at a time. The reason why is cause if you do to much, you won't know what fixed it.
I have also see fuel pumps intermittently cause low fuel pressure which can cause misfire codes. I have seen exhaust restrictions cause misfire codes.
So once you go through the air filter, I would then double check all spark plug tubes to make sure they don't have any oil. Then I would inspect the fuel system with a fuel pressure gauge and drive the car and see if fuel pressure drops when it runs ruff. Pressure should be around 56 Psi. Under acceleration around 40 psi
Do you have any more questions on this?
I use a special attachment to tap in by the fuel pressure damper on the fuel rail. I will then run the gauge up by the wipers and lay it there and monitor it while I drive.
I recently had a QX56 that had 56 psi when driving, but under wide open throttle it would drop to 20 psi and start to run poor. I actually took a video if you want to see
No, just the top engine cover. I would have to take a picture of the fitting I use. It's hard to explain
Remove the two 10 mm bolts, the attachment would then go into the fuel rail after you removed the damper. Then it will mount right on top of the attachment and two long 10 mm bolts are used to tighten everything down.
Yes, I have a liquid filled gauge if your wondering why it looks wierd
I need to get off line for the night. Did you have any more questions on this?
Since it is happening more frequently, that actually makes it easier to find.
I would start with the air filter. Something as simply as that could play a factor. Plus those K&N filters do take a toll on the MAF sensor. So I would certainly try that and see if there is a change.
The AC turning on and off is a load on the engine. So when the AC is engages, the idle is raised ( but may not seem it ) to accommodate the load. When you turn of off, then of course the idle operation would return back to normal.
If it only happens when stopped and in gear, I would try air filter and check fuel to start. If you had a scanner to monitor fuel trim. That would be the best way to see what is going on. Improper air and fuel trim readings can cause misfire codes as well.
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