Just want to share my experience with an amazing product that I discovered recently STP® Pro-Series Intake Valve Cleaner. If you want to clean your whole fuel system including the throttle bodies this product will literally replace professional fuel system cleaning in a mechanic shop that could cost you hundreds of dollars. Anyone with basic mechanical skills could easily perform this DIY. By the way, because our Gs has two throttle bodies instead of one bottle STP® Pro-Series Intake Valve Cleaner you need to buy 2 of them, for example, I bought two kits today in Autozone for 63 dollars. The product is self-dispensing and metering in your car throttle bodies, all you need to do is to lose the clamp on the intake tube that connected to the throttle body, slip an aluminum hook with a small plastic tube from a cleaner bottle inside the throttle body, reattach the tube and repeat all the above with the second TB. Then you turn the red dial on both kits first to "I" indicator and do the same with the blue one, start your engine, and in about one minute cleaner starts to flow inside. All you need to do at this time is to press the gas pedal to maintain around 2.500-3000 RPM in around 9-10 minutes. You could experience check engine light pop up a few times, do not worry it's normal, and it should disappear after all. Pull the hooks out, fully reattach your TBs, discard used STP kits and drive about 25-30 miles enjoying your perfectly clean engine. STP recommended performing this cleaning once a year. I just did it today and really blown away by the result. Here is the link to the product on Autozone https://www.autozone.com/fuel-and-en...ner/895149_0_0 and a video on how to use

You Tube

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Interesting!

Sea Foam comes with a clever hose, but it does not self-meter.

My only concern with intake cleaners is whether the cleaner, or the debris that it frees up, might poison the catalytic converters.

 

Its literally "freeing up" carbon build up. That's not going to hurt the cats.

 

Does it create a lot of smoke, like Sea Foam does?

 

It's created some smoke but it's much less than SeaFoam.

 

Since our engines are port injected, they don't have a carbon build up issue.
The fuel injector sprays down the lower intake and onto each intake valve, cleaning it as your drive.

Last year I was at the scrap yard to get an intake manifold and fuel rails from an 08 G35.
Once the manifold was removed, I could see the intake valves and I couldn't see any carbon build up and they looked perfect!!
Now, I don't know what the milage was, but the interior was very worn and most 12 year old cars probably have more than 150,000 miles.
Just something to keep in mind....

Now for anyone with a direct injected engine (most newer Nissan / Infiniti), this would be a useful product.

 

Port injected gets carbon build up too. It's just not as big a concern as on a gdi.

 

I'm not trying to put down your DIY. If you feel it is required then there is no harm in doing it.

 

Yes, but it can be handled with a $10 bottle of techron in the gas tank rather than a $60 kit that requires you to get under the hood

 

Even though the VQ37VHR is port injected, the entire intake tract downstream of the breather tubes, including the throttle bodies and upper intake manifold, will be dirty from oily crankcase vapors. Therefore, I think this is good for both port and direct-injected engines.

 

You don't really need a $60 kit either. A can of Seafoam will do the same thing as this, but it still won't totally eliminate the carbon. That bottle of Techron won't do what this, or the Seafoam will do.

 

I'd focus more on cleaning the throttle bodies and upper intake manifold. As mentioned earlier in this thread, the intake valves are being washed with fuel constantly.

 

Below are the intake valves from a wrecking yard, 2007 G35, after I pulled off the upper and lower intake manifold.
There was a fair amount of oil inside the intake. Oil was not "pooling" but it was covered with an oily surface.

I don't know the milage on the car, but I think it would be safe to say a 13 year old car would probably have at least 100,000 miles on it.
(Note: when I pulled up the lower intake, a little road dirt/sand fell into the intake ports. As you can see it on the floor of the intake ports and at the vale face.)



If you are thinking, the intake valves must of been have been cleaned in the past, here is a picture of the throttle body...
With a throttle body that dirty, I suspect the intake valves have never been cleaned.



For me, once I saw this with my own eyes, I thought there is no need to do any kind of "intake valve cleaning" all thanks to port fuel injection.
BUT I do clean my throttle bodies about every 30,000 miles.

As with any maintenance schedule, feel free to do what you think is required

 

Just to show the dirt on and around the engine, here is a pic before I started:

 

Yep, turns out gasoline is a halfway decent solvent and with the detergent additive you find in toptier fuel, even moreso. I think some people want to eat off the inside of their intake manifolds. It's really not a problem if there's some accumulation from the PCV system, the important bits are getting washed