I recently sold my AEM wideband to a friend and I helped him install it on his 350Z. His Z is a Greddy TT with test pipes on a stock block.

We had the bung welded on the drivers test pipe downstream from the OEM O2. Once we got the guage working it was reading super lean at idle (off the chart lean). We plugged the Cypher in and read the #1 O2 sensor on the drivers bank (narrowband sensor) and it was fluctuating lean/rich like it should.

We then moved the AEM O2 to the passenger side, by replacing the stock O2 sensor with the AEM sensor. The wideband reads perfect, and the stock #1 sensor fluctuates lean/rich with the AEM sensor.

This made us think that the OEM sensor on the drivers side had drifted a bit, so we replaced it. With a fairly new (but used) OEM O2 and the AEM back in the passenger side it still reads off the chart lean, while the OEM flucuates back and forth between lean/rich (indicating, at least at some point, its hitting 14.7:1).

The only thing I can think of that would cause this would be a leak in between the downpipe and the test pipe, but it doesn't sound like there is anything (we even used shaving cream). The AEM O2 sensor reads off the chart lean in both bungs on the drivers side, but works perefectly in the OEM bung on the passenger side.

Any ideas?

 

Not sure I understand your post KP... it looks like you started on the driver's side but then you "moved the AEM O2 to the drivers side" - and it read perfect... not sure what changed there to make it work based on what you wrote.

 

he meant we moved it to the passenger side and it seems to read perfectly. it's my car.

 

sorry, I was confused when writing that, but Merlin is right, we moved it to the drivers side.

I edited the original post for clearity and accuracy.

 

I can only think of a few possibilities based on what you've reported:

1. the leak is further upstream on the driver's side.
2. there is an intermittent wiring fault (harness related), which makes more sense to me since the stock narrowband appears to be functioning.

EDIT: now that I think about it, if it's a leak, revving the engine should eliminate any chance of sucking in outside air. if the reading does not go rich, then something is wrong with the wiring for sure...

 

Disclaimer: nooby here!

How is the car running?

If the depth of screwed in AEM O2 is the same in both OEM O2 bungs (B2 & B1) and the newly added bung on the driver side have no leak and entire B2 side have no leak, I would go someplace to confirm with the sniffer in tail pipes that B2 is lean and go from there.
It would be easier with Cipher if 2003 Z’s had WB.

Try running cylinder power test and/or fuel injector test with Cipher. Good luck

 

Or... that the driver's side bank is actually running lean.
Still running the stock fuel rail? Has it been removed recently?

 

I don't think it is possible that it is actually running lean because the stock O2 sensor shows that it runs 14.7 at least once ever 10 seconds (when it changes from rich/lean/rich).

The only thing I can think of is air is getting in to the exhaust from a leak. When you step on the gas it goes rich, this problem only exists at idle.

The car runs, we'll say that, but thats about all it does. We started retuning it tonight, and we've pulled a bunch of fuel out of the Emanage and we still need to pull more. As we pull fuel out the car is starting to run better and better. For now, we just have the wideband in the passenger side and both OEM sensors in the passenger side. We have also discovered that the rear sensors arn't being used, instead something is sending a signal to the ECU.

 

I re-read you post and it doesn't seem you tried putting the AEM into the stock location on the driver side. Correct? If thats the case... I'd suggest checking the bung you welded.
Throw the AEM in the stock location and see what happens.

 

We did put the AEM in the stock position on the drivers side. We tried the AEM in all three possible places (2 OEM, 1 aftermarket). In both bungs in the drivers side we did not get reliable readings, they both read lean.

We need to get the car in the air and retorque the flanges I believe. He is having some rattling issues that we can take care of at the same time.

 

I assume that you are putting the AEM sensor in the bungs above the Cats and not after the cats, correct?

 

there are no cats, the bung is in the testpipe