*I'll add pictures as I finish transferring them.

I can't post in DIY section.

For the past few months I've had this terrible lean problem that I could not figure out. I also refused to take it to a shop due to costs and I wanted to figure it out on my own. I did end up wasting about $300 for a new MAF and used O2 sensors. Hopefully, this can help someone avoid the same.

Well, I did figure it out ended up being the O-Ring between the brake booster and brake master cylinder. I'm awaiting the part it was 15 bucks! So, for now I taped off the vacuum leak with packing tape, lol. I might make a DIY for that since I will have to disconnect the master cylinder to make sure the O-Ring gets installed correctly.

Again, I'm not a mechanic or car expert by any means and this is going to be similar to my timing chain thread. I'm just going to put notes and steps on how I eliminated each cause.

Specific Tools:
Vacuum Gauge - Harbor Freight $15
Fuel Pressure Tester - Harbor Freight $20
S&D Auto Tool Fuel Pressure Rail Adapter- $40
Offset O2 Sensor - Harbor Freight $5
O2 Socket tool kit - Harbor Freight $50 (I only used it for what I needed then returned it, lol)
OBDII diag device - I have Consult III ($300 on aliexpress.com)
Various sockets

Testing your MAF

Proper fuel trim at idle should be 100%+-10%. My car was at a steady constant 135% at idle!

I got the following procedure from an Infiniti/Nissan technician and he said he uses this procedure correctly 90% of the time to find faulty MAFs. However, in my case my car was causing the same exact symptoms as a faulty MAF, so don't rush off buying a brand new one yet.

Basically, you run the car until it reaches operating temperature, turn it off, unplug the MAF, and then start the car, BUT ONLY IDLE it. This will set some codes, but you can ignore them and your short-term fuel trim readings should read: 75% or -25%. The car defaults to this setting and if there are any leaks the reading will not be set to the default. It would be in the 80% range or similar.

Checking for Intake Leaks
You can use carb cleaner or something similar, but I used unlit propane since I had that available. If you use unlit propane be sure to use some common sense here. Look for any changes in your idle. You can also use a spray bottle filled with water I heard and you can use a smoke machine, which I will explain later how to build for like 30-40 bucks and 30 minutes of time.

O2 sensors

Front

These are a PITA to remove and are located in the exhaust manifold. The connectors are on the valve covers towards the back firewall on the ignition harness. Prepare to get yours hands all jacked up if you remove these. A regular O2 socket won't fit here and I had some difficulty break them free with a 3/8 offset O2 socket as well. Unplug them first from their harness and then there is a little black tab that connects to the engine block. I was able to separate that tab by sticking a long flathead screw driver.

I went to Harbor Freight and bought their O2 sensor kit and used one of the adapters that fit on my 1/2 in breaker bar. They popped right off and then I returned the adapter set to Harbor Freight, lol. I'll leave that decision to you!

Then I used my 3/8 offset to loosen them a little more, but in the end used my hand with the socket. Installation was reverse, however, re-attaching the cables is a PITA here is a trick I did: attach a nut to a piece of rope and drop it down the engine bay, screw it around the harness connector and pull the string up carefully. Then re-attach the connector and you're good to go!

These are interchangeable, so you can try swapping them to see if your code moves banks.

Rear

They check how the cat is operating and shouldn't affect fuel trims. On my '06 Coupe these also ARE NOT interchangeable. The connectors were slightly different, so I couldn't swap places with them.

Checking Vacuum
There is a small port on the upper plenum where you can attach a vacuum gauge. It should be around 20-22hg I believe. Mine would jump to 22Hg, drop down to about 19Hg, and then back to 22Hg again. So, I started attaching my vacuum gauge to different parts to see if I got different readings and I did. I got 22Hg steady every where I attached the gauge except when my booster was connected to my engine vacuum. I then smoke tested just my booster and that is where I found the leak smoke was coming out between the cylinder and booster.


Fuel Pressure
*You will need a new O-Ring for the damper or buy a new damper. I have a new damper on the way; I plan on returning though. I found an O-Ring that will fit perfectly.

I bought the green O-Ring set from Harbor Freight for 10 bucks. The size of the O-Ring I used was: P007 1/4" x 27/64" x "5/64"

You can release the fuel pressure by pulling the 15A fuse in the IPDM and then crank the engine. I didn't bother to it doesn't spill that much fuel out.

I ordered this adapter:
http://www.autotoolworld.com/S-G-Too..._p_166673.html

I could not find a quick connect that would work with though, so here is how I modified it:

1. Remove the schrader valve.
2. Attach the small hose from the Harbor Fuel pressure kit to it and secure it with hose clamp to the end of the fuel rail adapter.
3. Attach other end of small hose to fuel pressure fitting and screw that onto the fuel pressure gauge.
I had a tiny bit of leakage, but it read the fuel pressure perfect and it should be at 51PSI.
*Might want to measure the distance between the adapter and flange. My damper flange sligtly bent when I secured it with the bolts and you probably want to put a small metal tube or something so that doesn't happen.


Smoke Machine
Oil Lamp Wick
Nichrome 32 gauge wire
Nylon Bind post
2 x 3/8 air hose fitting
3/8 vinyl rubing
RTV
mineral oil
Quart paint can
Wire leads

Perform the following:
1. Drill two holes in the lid.
2. Drill two holes on the side of the can.
3. Install the nylon bind post on each side of the can.
4. Wrap the nichrome wire around the oil lamp wick. Attaching each end of the nichromoe wire to the binding post.
5. I didn't have a big enough drill bit for the 3/8 adapters to fit through, so I used RTV to secure them and plug any air holes. I also wrapped RTV around the nylon binding posts.
6. Pour the mineral oil in the can, but not to much.
7. Attach wire lead from + battery to one side of binding post. Attach - battery to other binding post. Now your battery powers the smoke machine!

Then attach some vinyl tubing to the lid. One side goes to where you are testing and the other to an air compressor low flow of PSI or you can use your lungs like I did, lol.

Feel free to shoot me a message or reply if any of this is confusing or doesn't make sense, lol.

 

More pics.

 

do you have a part number or spot to where to buy the 0 ring for the brake booster and brake master cylinder?

 

Sorry, I don't remember the part number but I got it from the Nissan dealership. Mine has been able to pull up parts for my car pretty easily. It was about 15 bucks though to replace.

 

I just ordered that adapter to check fuel pressure much cheaper then ordering the AAM adapter block, i suspect i am dropping fuel pressure due to a bad pump and have been trying to figure out the most cost effective way to test it, thanks for the great post!