1997 Infiniti Q45 - Knock Sensors & Valve Cover Gasket Replacement

[ItsBry]

Hello! I purchased this Q45 about 7 months ago, I love these big body sedans! I didn't know this car and year could be so luxurious still. I used to own a '91 LS400.

Anyways, this car has about 178k miles on it. Not sure on the maintenance. Was told it has a slight oil leak, nothing serious. Gradually as the months go by, the leak has became bigger and leaves a significant puddle stain on the ground. The white smoke from the exhaust has gotten more and more. There's a smell of oil inside the cabin and outside the car. The driver's side valve cover has a very noticeable oil buildup, the passenger side looks to be dry. Coolant was pretty low so I added coolant. Ran the car, emptied out. I used that Bar's Leaks Head Seal Blown Head Gasket Repair and it seemed to patch it temporarily. The leak went away, the white smoke significantly got better. Then one day when I moved the car, I notice there was this dry patch of what looks like the sealant on the ground. Now the past 2 days, there is a knocking sound. I did get a P0325 #10 code as well. I notice when I drive the car, it feels as if something is wrong. Like its being held back. Acceleration isn't too great. Fuel consumption is pretty quick. Idles pretty rough. Car jerks sometimes when driving in the beginning. I seldom drive this car, I would say a weekend car at least.

I've been searching for YouTube videos and researching these symptoms and it seems like the knock sensors and valve cover gaskets leaking are a very common issue. I just purchased this Block Tester BT-500 Combustion Leak Test Kit, so i'll try it when I receive it. There isn't much out there for the Q45 on how to replace these so I was wondering if anyone here would happen to have some input. I really don't want to bring this to a mechanic to avoid something that can be a DIY, but if I have to then I will to save this car. So, if there are any picture guidance or something, I would hugely appreciate it. I want to keep this car and enjoy it as long as I can

Here she is btw :
https://ibb.co/NNNfbds

[3Q Jay]

Welcome to NICO.
First posts can be hard---sounds like you've got a lot going on.
Your priority should be to figure out the engine knocking
then the white smoke
valve covers eventually, but you can add oil for a while and figure out if she's toast or not.

and P0325 is for the knock sensors, which are VERY often melted/cracked by an overheat. And from your other symptoms, I'd say there's a pretty good chance you've had a significant overheat---but I'm only going by the info you have provided.
But do not confuse a bad knock sensor with a knocking sound from the engine.

[ItsBry]

Thanks for the reply!

Yeah I'm just frantically trying to figure out the problems and get to the solution. I recently just did a oil flush/change + new oil filter and the knock went away. Engine runs a lot smoother of course. White smoke appears to have disappeared. The next day I changed the air filter and let it idle for a bit just to turn it on every now and then, and there was no smoke whatsoever.

I had a P0400 code come up before the oil change however. Sooo i'm trying to see if the EGR valve needs some cleaning. Would anyone happen to know the size of this nut? Such a PITA.

https://imgbox.com/VeF3ObxC

[ItsBry]

Would anyone know what this part is?

https://imgbox.com/EkdbGk2s

I noticed this pretty significant leak underneath this

---

I just checked the EGR valve; the piston still works when I tested it. It doesn't look gunked up at all either. What else throws P0400 codes?

[3Q Jay]

your picture is upside down?
it appears that you are in the general area of the block "skirt" and oil pan. What specifically did you want us to look at?

Good that your EGR *valve* is not stuck......but that is only a small part of the system.
have you pulled it off and looked at the inside? not just the valve, but the pipe that feeds the valve from the exhaust, and the inside of the upper plenum (piccolo tube)?
See recent thread by fontana dan for some additional notes on this specific point.

[ItsBry]

Oops, sorry here it is in the right orientation

https://ibb.co/sv0rFjQ

The one circled in red. Is that some sort of drain plug or?

---

Yeah I was able to get the EGR valve off and inspect inside, its pretty clean inside. Still cleaned it out with carb cleaner. What exactly is a "piccolo tube"?

[3Q Jay]

not a drain plug. I believe that is the hex head for a tensioner pulley adjustment, covered in grime.
I see no harm in power washing a lot of this stuff. Just avoid getting electrical connectors wet. I like working on clean cars, but some people like getting greasy.

Looked thru my photos, but I don't see any of the detailed EGR cleaning exercise. the EGR valve comes off the upper plenum with two nuts as you know. on the intake side of that interface, there is a further removable tube (with the upper intake off) that goes inside the plenum and distributes the EGR gasses. That will be ugly as sin when you take it out.

[ItsBry]

not a drain plug. I believe that is the hex head for a tensioner pulley adjustment, covered in grime.
I see no harm in power washing a lot of this stuff. Just avoid getting electrical connectors wet. I like working on clean cars, but some people like getting greasy.

Looked thru my photos, but I don't see any of the detailed EGR cleaning exercise. the EGR valve comes off the upper plenum with two nuts as you know. on the intake side of that interface, there is a further removable tube (with the upper intake off) that goes inside the plenum and distributes the EGR gasses. That will be ugly as sin when you take it out.

Ah okay, thanks for that. Btw, would you know where the PCV valve is located as well? I should might as well try changing that out too.

[3Q Jay]

PCV, there are two. near the top of each inboard side of the valve covers. Driver's bank needs to be done while you have the upper plenum off. It *may* be possible to do without removing the plenum. But it won't be easy.

[ItsBry]

PCV, there are two. near the top of each inboard side of the valve covers. Driver's bank needs to be done while you have the upper plenum off. It *may* be possible to do without removing the plenum. But it won't be easy.

I think I've located them. I'll post pictures when I get chance. Thanks for your replies lately and help. Couple more things I'm trying to figure out; what is this in the picture? It is heavily saturate in what it seems to be oil

The red connector

https://ibb.co/x68qwsh

Close up

https://ibb.co/7CzQR1q

And all underneath it and around it is even more saturated with oil

[fontana dan]

You can do both PCV valves without removing the aluminum plenum. You will want to get 2 new valves as well as well the 2 grommets which seal the valves in the head.
PCV Valve p/n: 11810-6P000
Pcv Valve Grommet p/n: 11812-41B00
That red connector leaking oil...looks like the valve timing control solenoid (Part Number: 23796-6P00A). It probably has an o-ring which has turned into a flat piece of plastic. My '97 is leaking the same. Probably not your main priority right now.
Have you looked for leaking valve covers? If your VVT solenoid looks like that I would bet both of your valve covers are leaking.

[ItsBry]

The passenger side is dry but the driver's side looks like it. Not entirely around it, more in the front and where that valve timing control solenoid is. It's a lot of gunk.

I recently did the Block Tester BT-500 Combustion Leak Test and it didn't turn yellow, so not sure if that really confirms if there is a leak

[fontana dan]

Agree with Jay on washing the gunk off of the engine so you can find the source of the oil leak.
Is the car still losing coolant and having white smoke, along with the drivability issue?
You might want to do a compression test on all 8 cylinders.

[ItsBry]

Yeah planning to clean the engine bay up this weekend.

The car isn't losing coolant anymore but there is still white smoke on start up.

Especially on start up - rough idling, car jerks, smell of fuel/oil. Leaves a bit of a puddle overnight but I can't tell what it is. Oil level still good for now as well. But after warming up, the car feels fine and the white smoke goes away.

Fuel economy is totally garbage right now though, what is the culprit of that?

[98_Q45]

Late to this but:

I’m most familiar with all you mentioned. At over 300,000 miles: I have gotten my idle down to 625/650 and mpg at around 18-24 depending on traffic, heavy acceleration and a/c usage(could be better driving 65 versus 75-80, but older cars back then only had to be efficient enough for 65 mph and $1.00 gas lol, unlike this f*** foolishness of $3 and $4 and $5 gas today. It really makes your fuel economy look worse) I’ll say there’s a few things to look at that I had to contend with:

As for fuel mileage: the Q isn’t particular “efficient” even with everything I’ve done, but once you do it…it’ll make a big difference. What did so far fuel/idle related:

Spark plugs/boots
Later did coils chasing a hesitation issue
Injectors (not fun: other option is fuel injector cleaner but won’t fix leaking injectors)
Fuel filter
Both Fuel regulators (only because was having hard start issues)
Intake plenum gasket (was giving dancing idling issues and horrible vacuum leak/cold stall issues)
Throttle body cleaning

Once you do those, guaranteed gas mileage improvement. Of course, when the plenum is off, you can access most all of those. In my case, I was moreso chasing down and throwing parts at things, but it paid off because I was fixing and finding things that needed to be fixed anyway (like the intake gasket solved my crappy idle that I or other mechanics couldn’t figure out for years).

As for the valve cover, I would say it’s not “hard” because it’s straight forward, but it’s not easy either. Even after I replaced mine, it was seeping again it seemed. I ended up buying some permeatex spray n seal and put it all around. And high mileage oil/bars stop leak stuff will help rejuvenate the seals on the inside as well. I even noticed my spark plug seals had stopped leaking once I gave it a high mileage oil change AND drove it for awhile.

I wouldn’t worry about the knock sensor: I had that code as well, when in reality it was my bad coils causing it to trigger knock code.

I also regularly give my engine a good medium pressure hose down every oil change at least (at the car wash followed with spot free, don’t use regular garden hose water because it may rust things up and doesn’t give sharp enough stream to power off the grime). I cover up the battery and alternator and air intake, then just go ham lol. But not more than a couple minutes. Start up and drive for a bit to steam everything off. Never hurt anything. My Q engine gets quite dirty if left to its own too long. Last owners never cleaned anything and there was so much gunk couldn’t see anything. Sound of the wet fan clutch belt slipping, is a bit scary for a second though.

[PalmerWMD]

Yeah planning to clean the engine bay up this weekend.

The car isn't losing coolant anymore but there is still white smoke on start up.

Especially on start up - rough idling, car jerks, smell of fuel/oil. Leaves a bit of a puddle overnight but I can't tell what it is. Oil level still good for now as well. But after warming up, the car feels fine and the white smoke goes away.

Fuel economy is totally garbage right now though, what is the culprit of that?

Can you update us on the status of your car?

[ItsBry]

Late to this but:

I’m most familiar with all you mentioned. At over 300,000 miles: I have gotten my idle down to 625/650 and mpg at around 18-24 depending on traffic, heavy acceleration and a/c usage(could be better driving 65 versus 75-80, but older cars back then only had to be efficient enough for 65 mph and $1.00 gas lol, unlike this f**king foolishness of $3 and $4 and $5 gas today. It really makes your fuel economy look worse) I’ll say there’s a few things to look at that I had to contend with:

As for fuel mileage: the Q isn’t particular “efficient” even with everything I’ve done, but once you do it…it’ll make a big difference. What did so far fuel/idle related:

Spark plugs/boots
Later did coils chasing a hesitation issue
Injectors (not fun: other option is fuel injector cleaner but won’t fix leaking injectors)
Fuel filter
Both Fuel regulators (only because was having hard start issues)
Intake plenum gasket (was giving dancing idling issues and horrible vacuum leak/cold stall issues)
Throttle body cleaning

Once you do those, guaranteed gas mileage improvement. Of course, when the plenum is off, you can access most all of those. In my case, I was moreso chasing down and throwing parts at things, but it paid off because I was fixing and finding things that needed to be fixed anyway (like the intake gasket solved my crappy idle that I or other mechanics couldn’t figure out for years).

As for the valve cover, I would say it’s not “hard” because it’s straight forward, but it’s not easy either. Even after I replaced mine, it was seeping again it seemed. I ended up buying some permeatex spray n seal and put it all around. And high mileage oil/bars stop leak stuff will help rejuvenate the seals on the inside as well. I even noticed my spark plug seals had stopped leaking once I gave it a high mileage oil change AND drove it for awhile.

I wouldn’t worry about the knock sensor: I had that code as well, when in reality it was my bad coils causing it to trigger knock code.

I also regularly give my engine a good medium pressure hose down every oil change at least (at the car wash followed with spot free, don’t use regular garden hose water because it may rust things up and doesn’t give sharp enough stream to power off the grime). I cover up the battery and alternator and air intake, then just go ham lol. But not more than a couple minutes. Start up and drive for a bit to steam everything off. Never hurt anything. My Q engine gets quite dirty if left to its own too long. Last owners never cleaned anything and there was so much gunk couldn’t see anything. Sound of the wet fan clutch belt slipping, is a bit scary for a second though.

Awesome! Thank you for the reply

Finally have a chance to work on the car. I'm currently in the process of slowly taking apart the plenum, I wish I had a garage or space to work in

Going to change the spark plugs, ignition coils, knock sensors. I'll tackle the fuel filter next

Yeah planning to clean the engine bay up this weekend.

The car isn't losing coolant anymore but there is still white smoke on start up.

Especially on start up - rough idling, car jerks, smell of fuel/oil. Leaves a bit of a puddle overnight but I can't tell what it is. Oil level still good for now as well. But after warming up, the car feels fine and the white smoke goes away.

Fuel economy is totally garbage right now though, what is the culprit of that?

Can you update us on the status of your car?

Currently tackling these fixes, will report back!

---

Btw, does anyone know where to buy that rubber attachment from the air intake into the throttle body? Mine is literally falling apart.

[ItsBry]

So I replaced :

Throttle Body Insulator
Intake Plenum Gasket (BECK/ARNLEY)
Intake Manifold Gasket (BECK/ARNLEY)
Valve Cover Gasket (BECK/ARNLEY)
Knock Sensors (Replacement from PartsGeek)
Both PCVs (STANDARD MOTOR PRODUCTS from RockAuto)
Spark Plugs (G-Power NGKs)
Ignition Coils (DriveBolt from PartsGeek)

I'm no expert at cars nor do I try to be, but I'm willing to try and be a DIYer. Anyway I had trouble to even start the car. It cranks then POP. Happened like 6 times. After the car started, it had a very strong fuel smell then I also pulled up 3 codes which I never had prior to all this : P0110, P0120, P1120. I cleaned the sensors with electric cleaner spray and still did not go away. Disconnected the battery for a few minutes and unplugged the connectors and the codes went away but now P0300 comes up. I put back the OEM ignition coils and it still shows the code. Car has a very rough idle, strong fuel smell, alot fuel coming from tail pipe and a lot of white smoke.

I'm at a loss right now :/

[VStar650CL]

Did you maybe get a pair of coils swapped? The colors on the triggers should be:
1 - Yellow/Red
3 - Gray
5 - Gray/Red
7 - Blue/Red

2 - Red/Blue
4 - White/Red
6 - Purple/White
8 - Green/Red

[ItsBry]

Did you maybe get a pair of coils swapped? The colors on the triggers should be:
1 - Yellow/Red
3 - Gray
5 - Gray/Red
7 - Blue/Red

2 - Red/Blue
4 - White/Red
6 - Purple/White
8 - Green/Red

Oh shoot I did not know there are color coded, I atleast distinguished "driver's" and "passenger's" side lol, where is that marked? This is the ignition coil right?

[VStar650CL]

Those are the colors of the trigger wires. The power (White/Red) and ground (Black) wires are the same color on all eight coils, only the trigger wires are different for each cylinder.

[Ryantzer]

Btw, does anyone know where to buy that rubber attachment from the air intake into the throttle body? Mine is literally falling apart.

If you're planning to keep your Q45 you'd better get good at sourcing parts, because most of the factory parts are discontinued in the US through Infiniti dealers, and there isn't a lot of aftermarket available. If you're needing a part with no aftermarket options your best bet is to look up the Nissan part number on any of the online dealer parts websites or https://nissan.epc-data.com then Google the part number to find out where it's available. Amayama.com can still get a lot of the OEM parts for our cars from Japan but they're not cheap.