Unbootable

I have a 05 with front widebands, i bought the car used with the cats removed along with the secondary O2 sensors, No anti foulers installed & the car never threw a code, Cannot tell if it has a tune with CEL disabled !!!

No CEL codes, Checked with cipher & i found that the ECM is adding fuel ( positive short term fuel trims ) to adjust the mixture . Gave it some gas at idle and the ECU started to add more fuel, Bank 1 was adding 17% at about 2K rpm.

Car runs good cold, And in WOT. But, I have a problem with hesitation in low rpm ( part throttle ) , Anything less than 3K rpm.

I put a new fuel pump assembly from the dealer & a set of very low milage injectors but everything still the same. Checked for vacuum leaks, Swapped MAF sensor with no luck, !!!

Now, Secondary O2s are reading 0.28 ( all the time ) which is lean, Is it possible that the ECM is relying on the rear sensors to bring back the mixture to stoich value ?!!

Also, Anybody running without the rear sensors ( totally eliminated ) ?!!!

Thanks,

Unbootable

Here's a screen capture of the log file ,

djamps

iTrader: (1)

I've posted about this a few times, short answer is 'yes they can'. Not always but sometimes. In my case I was running pig rich and throwing lean codes when I had non-foulers. Pulling my hair out for a week until decided to stick the lower o2's straight into the exhaust stream and problem was solved ever since. My theory is that when there's a disagreement between upstream and downstream sensor readings, downstream wins...at least on certain years/models of VQ. More likely 04-05 where wideband upstream sensors were a new thing and not trusted quite as much.

Sounds like in ur case someone installed o2 simulators (which appear to be simulating a lean ratio) or you wouldn't be seeing any voltage with the sensors removed. My suggestion is to re-install the sensors directly into the exhaust stream and delete codes P0420 as needed.

Funny thing about my 03 Z is there are no codes even with test pipes and all sensors present, no non-foulers. On the other hand my 04 G (with factory widebands) throws p0420 even with HFC's. Luckily deleting them was easy enough in rom editor.

Unbootable

Good to hear that my theory maybe correct. I talked to a nissan tech, But he believes that they are only there to monitor the cats.

That's the weird part, I have no codes and i have no sensors or anti foulers, I jacked up the car and checked, But found both wires disconnected and zip tied to the brace under the car

I will ditch the no-name test pipes that i have and buy the fast intensions RHFC along with new downstream sensors, But do you recommend to ask them to add an extra O2 bung with no extension ?

So, could it be that the ECU will read the 0.28 Volts as a within-range value and that's why it's not throwing codes ?

Many thanks .

djamps

iTrader: (1)

I think you may have a hacked/flashed ECU if it isn't complaining about the missing sensors.

And with regards to the J-bungs, I imagine they would be worse than the 1" spacers that were causing me all kinds of trouble. Have normal bungs welded in for a few bucks at a local exhaust shop.

Unbootable

Any explanation to how the ECU is adding fuel but reducing the injector pulse ?

Is it possible to check with Osiris standard to see if the CELs are disabled ?

Just to be sure, You mean a bung like this ?

djamps

iTrader: (1)

Not sure about the reduced pulse, where do you see that? In my case I was having lean codes, but my A/F gauge begged to differ (it was cruizing at 11-12 A/F and wandering all over the place). Not sure about corrections during that time but it might have been going in and out of closed loop.

Don't think it's possible unless you've got a copy of the ROM file used to flash it. Dumping the ROM isn't possible unless you've got a pro-tuning license on your cable and uprev support enables dumping for you.

Yes, that looks like a standard bung. Most exhaust shops have them on-hand.

Unbootable

Many thanks for contributing in this thread.

Take a look at the attached log file ( revving at idle ), You will notice that the injector pulse is reduced while te A/F correction and rpm are increased !!!

You mean that the OEM widebands reading lean, While your aftermarket gauge reading rich ?

The fact that i'm getting high positive fuel trims on both banks that increases with the RPM makes me think it's not a vacuum leak, Sounds more like fuel or maf issue, But i put new pump and swapped maf and injectors with no luck !!!

Could it be due to having many breathing mods with no tune ?, ( headers, test pipes, catback exhaust, CAI, plenum spacer ) .

, Was planning to get an e-tune which is not supported with the tuner version !!!

djamps

iTrader: (1)

No, my aftermarket AND oem widebands read rich while the ECU codes thrown were lean codes. I'm fairly positive your issue is the same as mine, it's 100% sensor related.

Unbootable

I thougt for a second that it was a lean condition because of all the mods i have with no tune. But i will take your word for it and install new rear sensors along with fast intentions RHFC since the pipes i have are so raspy.

Many Thanks,

djamps

iTrader: (1)

There's no way any bolt on mods could really require more than 25% + or - fuel corrections needed to throw the code