In my G35 I just changed out my valve covers, spark plugs, and coil packs, oil and filter(5W-30) and ever since then I've been hearing this noise coming from within the engine. It usually starts to become noticeable from when the car is warmed up. I've tried looking through the forum and through youtube videos for something similar but they all sound different. I've had a "mechanic" hear it but he says it might be losing oil pressure, and sometimes the car will almost stall when idling in small moments. I'm not sure what it could be but I'd appreciate any help on identifying what it could be or if someone has had this problem before.

 

Hi Horsechoker,

My G does the same exact noise. I have a G35 07 coupe automatic with 80,000 KM (50K miles). This only happens when the car is in park or neutral. The sound goes away when I accelerate at park or when the shifter is changed to drive. The sound disappears as I rev. I suspect it is the heat shield but these usually are installed in the rear and the noise is coming from the front. I also think that the vibration frequency reduces when the engine is connected to the trans. In neutral the engine's natural vibrating frequency is elevated because the mass of the trans doesn't stabilize the engine. so it makes sense that the engine rattles when not connected to the drive train. But it is still annoying.

Check if the sound changes as you move from park, neutral or hook it up to the drive geard. Try reving the engine to see is you notice any rattle noise increase or decrease.

Maybe someone from the helps us out here.

 

Thanks for getting back to me. I took it to the Infiniti dealership for a diagnostic and they said that it's most likely that the previous owner didn't keep up on oil changes and that the aluminum head is a little bad and that the cam is riding at a bit of a weird angle so that's why. He also told me that it was nothing to worry about and to just keep up on oil changes. But it still feels weird to drive it like that.

 

It sort of sounds like a load of BS they fed you, low oil is going to wreck the bearings before it wrecks a lifter bucket. I would still pull and inspect the plugs yourself even if Infiniti checked them.

The cam is never going to "ride at a weird angle", it's held in place with it's bearing caps. Valve tick happens when there's too much gap between the cam and the lifter bucket which CAN happen due to improper oiling but there's a LOT of things that also fail due to improper oiling before the lifter buckets get ground down. Plus it's not going to affect just a single lifter bucket, that's a pretty loud tick and if it was due to oiling I would expect to hear half (or more) of the lifters ticking. Your video sounds like a single tick from one component.

 

Now it is possible that something broke on a single lifter bucket (most likely guess is the spring below the bucket on the valve cracked) but there's a lot of other things I would troubleshoot before pulling the valve covers.

 

I’m not sure if it would still be a bad idea to drive my car around since it is my daily driver. And it’s gonna be a couple hundred dollars just to find out the problem but at the same time it’s gonna need to happen soon.

 

Just drive it, check your oil level regularly and drive it.

Ask around with friends, family, co-workers if anyone is comfortable pulling your spark plugs to inspect for damage if you aren't comfortable doing it yourself. It's very easy on this car since the engine is mounted longitudinally (rear wheel drive), passenger/right side is completely accessible without removing anything, driver/left side only needs the intake tube removed then the coils/plugs are all accessible.

Plugs are 16mm socket and torque is 18 ft/lbs. Coil pack I think is a 10mm socket and the torque is 95 INCH/lbs.

Here is a link to the DIY on spark plugs, it's got pictures and is well written. I recommend using a piece of tape around the harness for the MIDDLE coil on each bank, it's easy to get them switched around and if you just wrap a piece of masking tape (or electrical tape) around the wire for the middle harness you won't get them flipped around.

https://g35driver.com/forums/engine-...ug-change.html

 

Thanks for the advice! I'm definitily going to be checking the spark plugs myself as it doesn't seem that hard. Is there anything else that I could troubleshoot to see what causes the noise? I just feel a bit uncomfortable driving it or pushing it, but it doesn't overheat and the noise goes away when the rpm increases either that or the exhaust is too loud. Also what kind of damage should I look out for when changing the spark plugs? Just normal wear and tear or something worse?

 

Here's a few pics to explain, what you want to look at in these photos is the blowby that's on the ceramic part of the plug, that orange/black ring at the base right next to the hex metal part. First one is what you expect to see on a normal high mile spark plug that's at the end of it's life. That orange-brown ring.



Next is a photo of one with significant blowby, sometimes this is caused by oil seepage into the spark plug well tube (something you definitely want to check for with a flashlight before actually removing the spark plugs), but typically this is caused by the plugs leaking gasses from the combustion chamber due to extreme age or poor manufacturing, or very very high cylinder pressures. I've heard in the past some kind of theory about the porcelain insulator becoming electrically polarized due to the high voltage (coil packs discharge at around 12,000 volts) but in all the plug testing I've seen for high performance applications with a much longer duration arc and much higher voltage (like pro mag stuff) the blowby is exactly the same so... I think that theory was eventually busted.



Next photo is what I'm HOPING you find, in this picture you can distinctly see one plug that is blackened all the way from the threads, across the metal hex, and up onto the ceramic. This is what a loose plug will look like, a significant amount of blowby is coming out of the combustion chamber around the threads of the spark plug, this is different than the previous photo where the gasses were coming up the middle of the spark plug between the ceramic and metal part. The plug itself tends to get very slightly sucked into and pushed out of the combustion chamber and makes a very distinct clicking sound, plus the sound of the gasses escape makes it's own unique sound.

 

I'm not sure if it's mentioned in that spark plug DIY I linked but the spark plug wells are very deep and you NEED to use some kind of plug socket with either a magnet (my favorite) or a rubber gripper, or you need to use a small separate magnetic pickup tool to remove the plug once it's unscrewed. I don't think a pair of needle nose pliers will be able to reach down the well tube.

The magnetic spark plug sockets are amazing, that would definitely be my first choice.

Also not sure if it's mentioned but always start the new spark plug by hand, take the ratchet off and screw it in by hand until it's seated, then use the ratchet (or preferrably torque wrench) to snug it down.

If you don't have access to a torque wrench in both 3/8 drive ft/lbs and 1/4 drive INCH/lbs then just give it a quarter to 3/8 turn once it's seated if it's the style with the little compression ring, if it doesn't have the ring then it's something like 1/16th of a turn, basically you just snug it down. Better to be a little loose than a little tight. The coil pack bolts are just barely more than snug, they break fairly easy so those are definitely ones you don't want to overtorque. Obviously the best option is to just use the torque wrench specs I posted earlier from the FSM.

You can buy a little squeeze packet of anti-seize and dielectric at the counter at most auto parts houses for a couple bucks, that way you aren't wasting money on buying a whole tube.