Hello everyone, I am the new owner of a 140k mile 2002 Q45, and am finding some issues that I could use some help with...

1.) This car accelerates very slow, it will maintain speed, but it just does not have the power to get there (quite a bit slower than my previous 140hp eclipse with 170k miles). I have a code reader and it popped up with the P0325 code - Knock sensor. I am fine replacing this, but I have read that a misfire or weak coil may cause the engine to knock (which causes the car to throw the code). I did not see any misfire codes, but are the coils something I should check as well? It seams like coils problems are common issues for the Y33 cars, what about for my F50? I have also heard that acceleration issues can be attributed to a bad fuel pump/filter. What is the likelihood of the fuel pump going bad at the age and mileage this car is at? I am averaging 18mpg in freeway driving (aka stop-and-go silicon valley traffic) if that is an indicator of anything. What should the fuel pressure be?

2.) Sounds like an exhaust leak from the driver side bank of the engine under moderate/heavy acceleration. My limited research tells me that this could be a cracked exhaust manifold. Are instructions available to remove and install the exhaust manifolds for the DIYer? Are the exhaust manifold to head gaskets prone to going bad?

I am very mechanically and electrically proficient, so I would rather work on the car myself instead of giving it to someone else.

Thanks in advance, Z.

Some quick notes from the y34 side.
1. The exhaust gaskets are not troublesome, but the manifolds themselves are... driver side especially.
It is possible to replace them and instructions are available in the FSM. Nicoclub provides them for free. Google - 2002 q45 FSM nicoclub - or something along those lines and you'll get there.

2. No info on the fuel pressure, but I haven't heard of many fuel pump issues with the f50 and y34. The y34 had a fuel gauge issue though. I feel like Nissan fuel components will throw codes pretty soon if they are having issues.
Your gas mileage seems decent if you ask me.
The coilpacks on these are not prone to failure either. When they start going out, you might get idling issues.
Have you checked your spark plugs?
If there truly is no other code, pretty weird to see the poor performance.

This is just my opinion and hopefully a true f50 owner comes along and chimes in.

Thank you for your response.

I have not checked the plugs yet, but I I plugged in my OBD2 scanner yesterday on my commute home and fired up the Torque Lite app on my phone. I set up the app to monitor the ignition timing and may have found the reason why the performance is bad. When cruising or under light engine load (low engine rpm), the ignition timing is anywhere from 10 to 30+ degrees advanced. When I step on the go pedal, the timing goes to zero as the engine reaches the mid to upper rev range. I am under the assumption that the timing should be "all in" or at least close to 30 degrees advanced when flooring it and with the engine under load.

This leads me to believe that the ECU is pulling timing under load. Its possible that this could be caused by a faulty knock sensor (I still have the P0325 code), but could it be a fuel pressure/flow issue not being able to deliver enough fuel, leaning the motor out, causing the knock, telling the computer to pull timing? Is there an easy way to determine fuel pressure? My OBD2 scanner does not read fuel pressure. Im doing my research before I dive in the engine to get to those knock sensors.

Any insights from the experts?

Also, What gaskets/parts are needed when replacing the knock sensors? I understand that the intake manifold will have to come off, so that is intake manifold gaskets at the very least right?

Thank you very much guys, Z.

You're dealing with more than I've had to deal with while troubleshooting my y34, but I can only answer one part with certainty.
You're right, that an intake manifold gasket kit is the very least. Those come in 3, but you can get away with only unbolting the intake where it meets the heads. You use the other gasket if you split the upper and lower intake.
And check the condition of all those hoses snaking around the intake.

holy crap, this car....

I am getting the "common" VDC/SLIP/ABS light maybe 70% of the trips I take (normally get the warning light about 10 minutes or more into a trip, it is not present at startup). I checked the brake fluid level, it is just above the full line. I dunno.

I also get the tire pressure warning light maybe 25% of the trips I take. I don't think the batteries are low because I can monitor the tire pressure of all 4 tires (set at 36~38 psi) at any time I want to except for when the light comes on.

And just today, the damn transmission wont shift from drive to park. I just commuted to work and when going to park the car, the transmission lock will not disable. I can pull gear lever out of drive and put it into neutral but it will not go into reverse or park. Also meaning that the key wont come out of the ignition. I shut the car down and restarted it several times, this time the VDC/SLIP/ABS lights are lit and do not go off and I still cant get the car into park. So my car is sitting in the parking lot now with the key in the ignition and the doors unlocked....

I am really missing the simplicity of my old aircooled vw bug converted to mazda rotary watercooled power.........

Instead of working, I have been trying to figure this thing with the transmission out. I think I fixed it!!

It turns out that the brake switch (the stupid hard to reach black one, not the easy to reach brown one) was out of adjustment (even though the distance between the switch housing and the brake pedal was within its spec of .7mm-1.96mm).

I took the switch out (rotated 1/4 turn counterclockwise per the FSM) and verified that the switch was working (normally closed ~ 0 ohms, and open circuit with button pressed) I reinstalled the switch with the switch housing practically touching the brake pedal. I tested it out and Viola! The transmission was able to shift into park and I was able to get my key! No more VDC/SLIP/ABS light on startup either. We will see if this switch adjustment will solve that VDC/SLIP/ABS warning light on my commute home.

Well I finally got around to replacing the fuel pump and filter yesterday, I figured that I should replace both as they probably never have been replaced before (147k miles now). As I mentioned in the first post, This car has NO power. Under very light throttle the car seams to have plenty of power but as I lay into the throttle, the car just falls on its face. The car has more power when the engine is cold, and has more power when in manual transmission mode in gears 1 and 2 only. When using the torque app I found that the computer was pulling timing so much that it was reading zero degrees advance (typically around 30 degrees advanced). This all starts to make sense, the computer is pulling timing due to the lack of fuel. When cold, the engine usually requires more fuel or at least the computer wont pull as much timing, although I cant really explain why in manual transmission mode the first 2 gears don't pull as much timing as in 3/4/5 or drive.

Anyways, I purchased my new fuel filter and pump off of amazon, both parts stated that they fit a 2002 infiniti Q45, and started the job...
1.) The fuel filter that says works for a 2002 infiniti Q45, didn't work for my 2002 infiniti q45. The original fuel filter is large in diameter, and the replacement was smaller in diameter. I thought that Amazon had messed up so I headed over to Orielly Auto Parts to get the correct one, and they showed me the exact same incorrect one! I showed them the one that came out of the car and could not get a match on it. They stated that Infiniti used the same (i.e. smaller one) filter on all q45s from 96 to 05. They told me to go to the dealer. Screw that, I will make it work...

Here is a picture of the original filter left, and the replacement filter right.


Here is the original filter mounted


Here is the new "replacement" filter mounted


To get this to work, I was able to bend the bracket holding the filter so that it would match the diameter of the filter.


Then I had to reshape the filter strap for it to work with the new filter


I cut off the excess material, drilled a new mounting hole and deburred all the edges


Here it is all put back together


2.) The fuel pump that was supposed to be a direct replacement for a 2002 q45 is not a drop in replacement for a 2002 q45.
Here is a picture of the old pump on the right, and the new pump on the left. The look pretty much the same....except, the inlet on the bottom of these pumps are shown on the bottom left side.
The factory pump has the outlet on the top LEFT side, the replacement pump has the outlet on the top RIGHT side. Basically the factory pump has the inlet and outlet lined up with each other, and the replacement pump has the outlet on the opposite side of the inlet.


Mechanically I was able to mount everything up, but when I went to plug in the fuel pump wiring....The damn wires were about 6mm (1/4") too short! Because the orientation of the pump outlet, the wiring connector of the new pump is now on the opposite side and further away than the original. Good thing the pump came with wiring that was a little longer, So I desoldered the original wires and soldered on the new ones.


I reinstalled everything and got the car running. This is like a totally new car! It actually has power! I know I still have to replace the knock sensors, but holy crap, this car moves and it does so much more effortlessly.

congrats

Hey Zen I wish I coulda talk to ya sooner there are not that many issues with nissans pumps, but with that said all mech parts start to lose efficiency and performance over the course of many miles and many hours of use. I got my 02 with 223k on it and decided to replace with new as well. I too got the wrong fuel filter off ebay was told it was a factory and like you found out it was not correct, took it to infiniti and they got me the right one. I know the factory pump is very expensive but if they can last 223k no probs i was definitely replacing with the same pump and found a nib factory pump on ebay for 70 bucks. Anyway it does run much better after i switched it out so good for you for doing so.

I also recently rebuilt and upgraded my spare 4.5 motor and installed it and man oh man its amazing u should check out my thread saying 02 Q45 upgrade lets see what she can do .... for more info. But after getting it all into the car I too got the P0325 code and my car sucked at first i was livid but found out if the code is there it will take all timing out of the car so as to save the engine. I lucked out not only did I have the intake manifold gasket and a spare harness and knock sensors from my old motor, but it ended up just being a very dirty connection so I didnt even need to change them. Cleaned out the connector and reconnected it cleared codes and have been driving for weeks now and code has disappeared. Knock sensors need a very good connection and so they are prone to coming on for stupid reasons. Check this first if not it removing the intake is not all that bad but has to be done to get to the 2 sensors that are in the valley underneath. But once that was fixed car was a raped ape beast machine.

As for why it has more power in manual mode its because the motor gets more torque an power as well as shifting at a higher rpm than normal. I assume it has less torque limiting factors as well in manual mode. But I did procure a middle east ecu and had it coded to my key and according to some info i could find their rated at 365hp over there and 355 tq. My car revs to 6800 rpms everytime in manual mode and pulls sooooooo hard.

I am working with a few people trying to get someone that would be willing and capable to retune our earlier 02 computers and maximize the engine for us. I am also still working on getting the headers to work so far first attempt was not good but not giving up yet. I did port out the factory headers to max flow and then added more structual support welds to help them from cracking. I had a nice amount of cracks on my drivers side so had to do lots of work. I also removed the 2nd set of cats as they are not monitored and really not needed imho, and removed 3 of the 4 mufflers leaving just the big rear one and eliminating the exhaust valve and adding an xpipe. Made a HUGE difference making the entire exhaust using 2 1/4 pipe on both sides. Also replaced the rear end pumpkin which has 2.7 gears with a pumpkin from an 05 which has 3.2 gears and that made a huge difference as well in acceleration with no side effects.

If i can be of any more experience feel free to pm or post

Thank you for your insight. Yea, I know genuine nissan parts are best but amazon is so damn convenient... I guess thats why I had to deal with this mess. Anyway The car feels much better now, although I still feel the difference in the way the engine performs when in manual mode between gears 1/2 and 3/4/5. Q45-02 I believe that you are correct, the cars acceleration feels like the computer is still pulling timing due to that knock sensor (like it should), So I intend to get both of them replaced soon. My only other question is what other parts are needed for the knock sensor replacement? I understand that I need an intake manifold gasket set, is there anything else?

No intake manifold set is pretty much all u need to have if u need the sensors and a harness I would be willing to work out something for mine if u want them I know their pricey. But if I were u try taking the connector off which is right by the green passenger side upstream connector which is on the rear of the head just behind the valve cover. Its a black connector and not to bad to reach just disconnect clean and reconnect and clear codes and see what happens you'ld be shocked at how easily a lil dust can effect them. But if you do need to remove the upper intake isnt all that bad just make to remember the lil 12mm bolt on the back half for the fuel rail it has to come off first before u can get to the back bolts. The harness is a pain to get out of the way but take it slow and easy and itll be fine.

Finally getting around to putting in the new knock sensors (P0325 code) and look what I found!



A rats nest! Literally where the knock sensor harness is (in the valley of the engine block. Picture is with the upper and lower intake manifold removed). Also shown is the eaten through knock sensor wire harness.



Here is a photo showing the brocken wire harness removed,

So now I need a new knock sensor wire harness, anyone know what the part number of a 2002 infiniti Q45 knock sensor wire harness is?

Damn, quite a trip with this car!
http://coulterinfinitiparts.com/nissanp ... 24079AR000

24079AR000 is the number you're looking for. It is the same one for some other Nissan V8s and if you don't like their price, I most probably have one from a 2004 M45 that you can have for the grand sum of $0. Just pay S&H

I want to say thank you all for making the forum such a wonderful source of information.

My 02 Q45 have exactly the same symptoms : lacking of power, throwing P0325 code of knock sensor.

So I am planning to replace my fuel filter soon. ( will do the fuel pressure test first of course) and replace the knock sensor if things doesn't change.

So I want to know:
1. did you change the knock sensor eventually? Does it improve the engine performance?
2. do you happen to have pictures of the knock sensor replacement? any tips?

Thank you again!