? for the fuel injection experts.

[a4turbo_2002]

Could my intermittent lean condition on bank 1 be caused by a rear o2? Its not a vac leak. I was told my stage 3 tune had rear o2s coded out... so i removed the rear o2s... well they are definitely not coded out iv got constant multiple rear o2 codes. Iv got some surging and slight misfires all at partial throttle. Wide open it runs fantastic, but everytime i get the lean condition i just dont drive it until i think i fix a vac leak and it goes away for a week. Last night on nefmoto i was reading over some general 2.7 fuel inj. Stuff and came across o2s,. According to bentley the rear o2s are not for emissions and catalytist condition analysis. I will post the quote from bentley below

[a4turbo_2002]

Oxygen sensor control behind the catalytic converter is responsible for final control correction. It is the primary sensor and can override the signal from the oxygen sensor control before the catalytic converter.

Oxygen sensor control behind catalytic converter is superior to *oxygen sensor control before catalytic converter and is the primary control. It corrects slight changes in the mixture (i.e. enrichment or thinning) by holding oxygen sensor control before catalytic converter at its highest or lowest point for a specific time (duration). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich- direction. If this time is in the negative range (i.e. 50 ms), mixture is shifted in the -lean- direction.

[Monty23]

If the rear O2 sensors are physically disconnected, the ecu will not try to use them. This issues is either an air leak somewhere in the plumbing between your MAF sensor and your cylinder heads, or your tune is not correct (MAF calibration). What do your fuel trims look like?

[a4turbo_2002]

Ok, well il keep looking for leaks... pissin me off iv been looking for the longest time! Thats literally rhe only thing i can think of that changed that i havent tried yet, ran great stg1! But my idle fuel trims were really rich on bank 2 at idle last time i checked.. like -10% but that was before the lean code came back, i wqs actually just tryin to sort out my cyl 4 5 and 6 missfires... il post more data today after work on fuel trims so check back lol

[a4turbo_2002]

Starting to wonder if its the pcv valve

[Monty23]

Have you sprayed flammable brake cleaner or engine starter around you engine to try and find any leaks? have you pressure tested you plumbing?

[a4turbo_2002]

Pressure tested, tried propane and brake cleaner... but if its internal like a bad check valve il never know

[a4turbo_2002]

Bought new icms and still have misfires on 4 5 and 6... wonder if its related

[julex]

lean code means that car has reached its adaptation limits. It could be O2 sensor itself getting old and crabby, it would be possible to identify by sticking wideband in there or going to place that has one and can stick a probe in the exhaust to what it coming out AFR wise.

Second culprit is your intake. Now, are trims -10% for both banks or just one? If one... then I would sat it is O2 sensor or injectors. If both... check your maf - provided you don't have a significant leak like though old and tired diverter valves (they develop leaks with age).

[julex]

If you're getting misfires due to mechanical issues then it would be natural that as a side effect your exhaust is lean since it never ignited :)

[a4turbo_2002]

lean code means that car has reached its adaptation limits. It could be O2 sensor itself getting old and crabby, it would be possible to identify by sticking wideband in there or going to place that has one and can stick a probe in the exhaust to what it coming out AFR wise.

Second culprit is your intake. Now, are trims -10% for both banks or just one? If one... then I would sat it is O2 sensor or injectors. If both... check your maf - provided you don't have a significant leak like though old and tired diverter valves (they develop leaks with age).

Primary 02s and diverter valves are brand spnkin new:/ trim was only negative on the bank with a misfire.. which makes sense

[a4turbo_2002]

Maf is also brand new, maybe 100 miles on it

[a4turbo_2002]

lean code means that car has reached its adaptation limits. It could be O2 sensor itself getting old and crabby, it would be possible to identify by sticking wideband in there or going to place that has one and can stick a probe in the exhaust to what it coming out AFR wise.

Second culprit is your intake. Now, are trims -10% for both banks or just one? If one... then I would sat it is O2 sensor or injectors. If both... check your maf - provided you don't have a significant leak like though old and tired diverter valves (they develop leaks with age).

however like i said, my lean condition did go away for awhile then i rotated my injectors 90 degrees and now its suddenly back.. wonder if i disturbed an injector o ring or the harness somehow.. somehow i still think its the same issue from before

[a4turbo_2002]

If you're getting misfires due to mechanical issues then it would be natural that as a side effect your exhaust is lean since it never ignited :)

I dnt have misfires on the lean bank...

[a4turbo_2002]

I dnt have misfires on the lean bank...

I also have stock ics.. and it was a 60 degree day when it happened.. i was waiting till it warmed up to get a front mount and its getting there so maybe it was tryin to correct for hot ass intake air..

[julex]

you need to do proper bosot leak test with tons of water+soap sprayed all over the engine and be vigilant for any air escaping anywhere.