2009 Nissan Murano - Complete overhaul - misfire

I have a 2009 Nissan Murano with a 3.5L v6. I am the only owner of the vehicle. Back in November of 2021, I completely dissembled and overhauled the entire engine. The oil rings had gone bad after 210,000 miles and the engine was running very poorly. I replaced the following items:

All gaskets
All bearings
pistons (I could not fine the original oil rings so I had to change the pistons to accommodate new style of oil rings.)
piston rings
timing chain assembly, water pump, oil pump
Catalytic Converters - Both sides
fuel injectors
spark plugs
2 of 6 coil packs
I replaced the old engine wiring harness with a 2012 harness that I have completely checked out for integrity. I don't think we have a wiring problem.

After cranking the engine for the first time since the rebuild, I've experienced a noticeably misfire with a P0304 code. I pulled the spark plugs and realized all the plugs on bank 1 looked perfect and all the plugs on bank 2 looked lean. I checked fuel pressure and it read 48psi at idle. Spec. said it should be 51psi at idle. I replaced the fuel pump and checked fuel pressure. It is basically the same at 48.5 psi....and I still have a misfire. Does 3 psi make that big of a difference??? And if it does, I guess the new pump is also operating below ideal??? Or, do we have some other problem causing low fuel pressure? Does anyone think the misfire is from something other than low fuel pressure?

I thank everyone in advance for all of their help.

David S.

I forgot to mention that I did a compression check and I had 11:1 across the board.

Hey dsorjonen! I honestly think the best thing you can do is start from a clean slate. Approach the misfire like you've never seen this vehicle before.

First off, when does the misfire occur? At idle only? While driving only? All the time?

#4 is up front and easy to access. Pull the coil out and check for spark strength AND leakage around the coil boot. Move the coil and plug from #4 to #2 or #6 if there's any doubt.

Check #4 injector for power and injector pulse with an incandescent test light.

You've already checked for compression, which is excellent. Would you mind sharing the exact compression values for each cylinder?

Does 3 psi make that big of a difference??? And if it does, I guess the new pump is also operating below ideal??? Or, do we have some other problem causing low fuel pressure? Does anyone think the misfire is from something other than low fuel pressure?

IMO, 3 PSI won't account for your single cylinder misfire. That may be *A* problem but not *THE* problem. There are other ways to get low fuel pressure out of a new pump, but lets come back to that later.

dsorjonen wrote:

I forgot to mention that I did a compression check and I had 11:1 across the board.

You've got some work into that one, good man
I've never expressed the results of a compression test in a ratio before.
Could you please elaborate?

Hey Tyler,

Thank you for your reply. Okay, from the top........

The misfire occurs at all times other than initial start up. For about the first 20 seconds, maybe a little less, the engine does not have a misfire.

I have performed all those procedures regarding coils and plugs many times checking my work. I have good line, ground and signal on all coils. I've moved them left right and all around. I've put a test light on signal and pulsed as it should.

I have tested power and injector pulse and they also seem to be fine. I haven't double checked the injectors and I will do that tomorrow.

Compressions was spot on 11:1 on all but one cylinder on bank 1 and it was something like 10.9 to 1


One thing I think is important is that all of the spark plugs on bank 2 look lean. All the spark plugs on bank 1 look good. I'll pull the plugs and take pictures tomorrow.

Quick answer... Low fuel pressure would affect all cylinders with a lean condition. I'd be more inclined to think a gasket leak on bank two as all those plugs showed lean.

Having fuel trim data and freeze frame data would help diagnose the problem better.

Hey Noah,

Sure, 11:1 is simply 11 times atmosphere (14.7)....so right around 160psi.

Scannerjohn, I agree with you that low fuel pressure would cause all plugs to be lean........but I have one concern with my arrangement. The injectors on bank1 are are in-line with the main fuel line coming into the fuel rail. The fuel rail for bank 2 branches off at a sharp 90deg "T" junction and then bends another 90deg towards to the other side of the engine. Do you think it's possible for bank 1 to have more consistent supply than bank 2? Maybe that's a stretch.....idk.

I'll certainly check gaskets tomorrow to see if we have a leak somewhere. This is a complete rebuild and I did check my work many times as I went. I've rebuilt something like 15 different engines and this would be my first gasket to leak...but hey, It could happen and I'll check.


I'll get fuel trim data tomorrow. I've checked it over the weekend and bank 1 had zero LT and basically zero ST fuel trim. Bank 2 had zero LT and something like 5%+ ST

I'm basing my opinion about your fuel delivery question on the assumption that the system is OEM. Unless their is an internal restriction, fuel pressure and volume would be equal. You replaced all the injectors so unless the flow rate of the injectors in bank 2 are different than bank 1, you should have equal fuel delivery to both banks.

The static fuel trim of +5 on bank 2 points to a lean condition but dynamic trims will tell more. Increase RPM to 1500, 2500 and 3500 and note trim values at each stage. Growing positive Better values are indicative of a vacuum leak but you have two banks to observe so let's see the results. Freeze frame info on when the P0304 sets helps as well. If you know these testing procedures, I offer them to be on the same line of thinking and understanding. Noah and Tyler are two who have invaluable insight and expertise well worth following. I look forward to reviewing your results and progress.

VegasJAK wrote:

The static fuel trim of +5 on bank 2 points to a lean condition but dynamic trims will tell more. Increase RPM to 1500, 2500 and 3500 and note trim values at each stage. Growing positive values is indicative of a vacuum leak

I disagree with this. With a vacuum leak, fuel trims tend to improve with elevated RPM's. Growing positive values would indicate a fuel delivery, or air metering problem.

dsorjonen wrote:

Do you think it's possible for bank 1 to have more consistent supply than bank 2?

An injector balance test would not be a bad idea.

Chad, you're right. I wrote that wrong. Ment to say better. Thanks for correcting that.

Chad / Scannerjohn

Here are screen shots off my phone as I graphed ST fuel trim.

The RPM at the time of the screen shot is in the file name.

Image with file name 900 is at idle. The misfire occurs exactly when fuel trim is increased. Every once in a while the engine won't misfire for two or three seconds when at idle. 95% of the time at idle is the pattern you see in the picture.

There was no misfire from RPM 2000 to 3000.

The image with file name "3000 to 5000 to 900" is when I held steady at 3000 then did a quick throttle snap up to 5000 and then foot off the throttle back to idle. I held steady until 16:13:56 and was on and off the throttle before 16:13:57....the U shape formation. The rest of the graph is at idle with the engine trying to recover. The engine did not misfire until I gave it quick throttle snap.....and then started misfiring immediately when it went back to idle.


I tried to graph RPM on the same chart but I can't show two different Y axis and the scale is way off. I don't have any fancy dancy scanner equipment like you big dogs.....bowwow.


ALSO, I've been working through this issue for about three weeks now. Once I identified this pattern, I moved all of the coils from bank 1 up to bank 2 and vice versa. No change in performance. I then moved all of the injectors from bank 1 over to bank 2 and vice versa.........SAME PROBLEM....NO CHANGE.

dsorjonen wrote:

I don't have any fancy dancy scanner equipment like you big dogs.....bowwow.

With that in mind. Swap all bank 1 injectors with bank 2. Repeat RPM test. Does bank 1 now run lean?

Please see my edited response. We were thinking the same I guess.

So I see why you're thinking is directed to the fuel rail for bank 2.

Right now the only thing I can come up with is that there is some small obstruction inside the bank 2 fuel rail. I'm going to take the fuel rail off and give it a very thorough look over to see what I can see. I'll keep you posted.

I went back and re read your posts. I did not see any mention of testing, swapping or replacing 02 sensors. You gave trim values but look at the B1 and B2 sensor voltages. Graph those. What I'm thinking is the heater circuit on the B2S1 sensor is not working. When you run up the RPM the exhaust is what's heating the 02 to it's operating temp and it starts producing the correct voltages. When you go back to lower RPM the 02 goes lean.

Yeah, I have not paid much attention to the O2 Sensors, and that certainly makes good sense. I'll get some data on those and circle back tomorrow.

Thank you again for all of your help with this.

dsorjonen, I grabbed your 900 RPM capture because you mentioned that the misfire occurs when the fuel trims increase.



I see an average of 10-20% positive increase during the miss. Shooting from the hip, that makes me wonder about an injector problem. :huh: Not a restriction, more like an electrical problem. High resistance, poor contact, like that. Probably not an injector, since you already moved those around.

"Shouldn't that set an injector code?" Well, I searched service information for this '09 Murano. There are no injector codes. In other words, the injectors are not electrically monitored by the PCM.