Hey guys I been trying to track this problem down for about a month with no success! My car has been throwing a P0171 code at idle for the past few months. I have tried several things to fix it, but nothing has worked! I'm literally losing my mind and trying to get anyone else's input in what else to check.

The car has no power loss and responds really well.

The car idles between 650+-50 pretty constantly, however, it runs a little rough when the ECU tries to reset the short-term fuel trim levels. I also have extremely terrible gas mileage; I'm talking between 10-12 MPG. At idle the fuel trim is at 135% for both bank one and two.

I have done the following with no success:
Installed Z1 Motorsports silicone hoses all connections are snug.
Put some SeaFoam in hoping to spot some leaks I missed. Didn't notice any.
Replaced Y-Pipe, mid-pipe, and had the mid-pipe welded to the muffler.
Bought a brand new OEM MAF no change.
Swapped both front A/F sensors with used OEM sensors same result.
I even took off my plenum spacer to see if that was a problem nothing changed.
I went around the intake tube and intake manifold with unlit propane no change at idle.
Power balance test engine responded to every fuel injector test.

Hooked up my vacuum gauge to the intake manifold. It reads ~22hg, drops down to ~19hg (When ECU tries to reset A/F trims to 100%), and then raises back to ~22hg when the trim returns to 135%.

Currently building a DIY smoke machine to see if I can find any vacuum or intake leaks. I haven't tested fuel pressure or anything like that though.

Anyone have any other ideas? I'm trying to think outside the box...

Here are some screenshots from Consult 3:

IDLE graph: http://s50.photobucket.com/user/coff...DLE-1.jpg.html
IDLE: http://s50.photobucket.com/user/coff...dia/1.jpg.html
When Idle drops: http://s50.photobucket.com/user/coff...dia/2.jpg.html
Revving at 3K for 5 mins:
http://s50.photobucket.com/user/coff...FTER2.jpg.html
http://s50.photobucket.com/user/coff...FTER1.jpg.html
FreezeFrame: http://s50.photobucket.com/user/coff...P0171.jpg.html

 

Well, I made a DIY smoke machine for about 30 bucks. If anyone is interest or wants me to post up how I did it let me know.

My brake booster is causing a vacuum leak messing up my A/F ratio. I attached my vacuum gauge next to the pipe it connects to and got better readings. Hooking the booster back up would cause the readings to max out. I recently purchased the AAA extended warranty, so hopefully I can get this covered.

I highly recommend buying a vacuum gauge if you don't have one! It's 15 bucks at Harbor Freight. I could have saved myself $375.00 in parts I didn't need, since it showed all the same symptoms that are used to replace MAF sensors.

Now does anyone need a brand new MAF or four used O2 sensors from an 06 Coupe?? LOL.

 

Put it up under tech DIY under Intake issue troubling.

 

I don't think I have permissions to post there.

 

Did you find what caused the brake booster to leak?

 

yes there was a $15 o-ring between the firewall and the brake booster itself.

 

I'll have to look into this. I have the same code being thrown and trying to figure out the culprit. For the longest time it had issues starting, but no MIL/CEL would come on until now. I figured it was the fuel damper on bank 1 so got that replaced. Working on getting some miles on it to see if the MIL/CEL comes back on.

Where did you get the o-ring?

 

I bought it at Nissan. Do you still have problems starting? I'd start with the basics: air, fuel, and spark. Check for vacuum leaks and power balance test.

It could be your maf too try cleaning it. If you need a new Mac I have a brand new OEM I can sell cheaper then the dealer.

 

Yeah I still do. But it's very inconsistent. Some times there is a delay and others is instant. Very odd.

Going through the service manual to try and get some ideas.

Cleaning the maf is next on the list.

 

good stuff. i have this code as well but no issues.

How did you get your hands on consult 3? Please link me.