Today I am getting a new heated GM/Delco 02 sensor installed. Old (5 years) non heated Bosch appears functional but not confident it is reading true. Will verify no leak at header flange to exhaust pipe affecting my reads. I retightened the flanges before storage last season. New quality copper gasket used there. fuel filter was replaced last week.

I am starting from scratch with my EBL tune. I recalculated my BPC and it comes to 81. I will use that even though i could not do so last season. 80 lbs inj at 23 lbs FP - 350 CID. I currently have my BPC set to 115 as both VE tables were over 100 in some cells repeatedly after multiple VE learns. I think i upped by 5 after each Learn session till i arrived at BPC 115 and < 100 for fuel table.

What I am finding is that having a fudged BPC is affecting my OL idle A/F(very lean). I am seeing OL 02 sensor read 25-100 volts at idle? WB shows 16.0-16.5/1 even though I am much richer in my Ol AFR CTS VAC table. Is there another setting other than that table to command a OL idle A/F? Because of lean idle(WB02) i also funged that table to get A/F to drop. i dont think that is appropriate, and besides it did not help. Possibly my AE as well as PE values are getting affected as well due to BPC being fudged. Seems that i am not getting repeatability in my tune. By that i mean each day it differs(today BLMs shot high to 145) and i appear to be chasing my tail making changes without seeing positive results.

Will be adding the VAFPR(ready to plug and .bin waiting) but it appears I have issues that that wont help.

 

I kind of had the same issue- one day it would do this, the next that (VE Learn sessions). until I replaced both header collector gaskets and replaced my intake manifold gaskets. Since I didn't use loctite on the intake man. bolts, 6 out of 8 were loose. and i mean loose. Now it's on the money. Maybe something mechanical?
sorry dude- didn't catch that you already replaced those gaskets.
hey, let me know how that IAT hookup goes- I want to do that

 

always a possible vacuum leak but unlikely as i already checked that.

the header flage/ext pipe did loosen but we added new lock washers and should not reoccur withing one month of use.

will check again.

 

I can't offer a reason why, but I have fudged the BPC as well. I hit 100 in the VE tables right off the bat. I ended up taking the calc'd BPC and mutiplying it by 1.72 to get the VE under control.

Seems like I have the exact same problems you do...as a result my VE tables look really screwed up. The good thing is it drives smooth. I do get a few stumbles and bogs on a warm restart tho...

 

Thanks V8. However are not some of the OL calcs done off the BPC without regard to the main fuel tables values? Meaning if the BPC is 113 vs 81 that is a huge difference(40%) when the ECU does its calculations. A 113 BPW is suggesting the injectors are smaller or the engine is smaller or the fuel pressure is lesser is it not? with that the fuel delivered is much greater.

anyone else care to offer up an opinion?

when i get the car out tonight with my 81 BPC i bet the BLM's will in excess of 160 pegged max.

 

Ronny

I had somewhat similar problem to yours, albeit different. In my case, in preparation for TBI conversion I’ve installed NBO on the right side exhaust and WBO on the left side – dual exhaust system with crossover aft. The WBO was reading 13.8 – 14.0 at idle while NBO was reading 150 to 250 mV. Swapped sides – now NBO is reading about 700 mV and wide band is reading around 16.5.
Nothing was apparently wrong, but I pulled a stethoscope and listened for leaks – found a hairline fracture in the tube to header flange weld. Reworked questionable weld, new gaskets, re-torqued header bolts – problem was gone.

//RF

 

update. there were no dicernable exhaust leaks with car on lift. at that time a 3 wire GM NB02 sensor replaced the Bosch unit. Car runs Ok now that I have the AE back in line(was overly rich) and still am running the "fudged" BPC at 113 vs 81. I gues the fudged BPC is acceptable practicve? CL is almost instantaneous and I will say possible runs a bit better in that regard. BLMs in line with no major changes there due to NB02 swap to heated.

a word of caution on WB sensor. i have taken all precautions to prevent damage to sensor. I have car wired so that the sensor is not pre heated until engine is running. also wired to prevent sensor or LM1 unit from experiencing any starter voltage spikes. another precaution i did is to add a heat sink($85!) to pull sensor out of exhaust stream. sensor is after header flange at 2 oclock position in ext pipe. Innovate does not dispute the issue that deveops of repeated sensor failure. they suggested removing after each use and only use on warm engine to prevent damage from excessive condensation. i think the excessive moisture and cold temps here may have killed my sensor too often. no WB for me till I replace unit again($50).

 

Ron,

I didn't have a discernible exhaust leak with car sitting still. It was only when I ran into low rpm/low kPa which particularly occurred with a high decel situation. It shows up with EBL Learn with EBL continuing to add fuel in those areas. If you look at the VE Learn I've attached it shows up with all the 12% adds to the VE. Now that I've "fixed" the leak at the rea of the exhaust system, VE Learn is now reducing those same areas.

 

Dom:

I will look there as you indicate. does not the car go to OL tables on a lift of pedal where the TPS is <3% ? Should not the EBL Learn correction disregard any 02 feedback in that scenario? I do believe my BLM-INT is somewhat rich at any at MAP under 35-40 and RPM 1600 and under but I dont believe my Learns are continuously adding fuel there. Also I dont think it is easy to be CL down there is it? In fact I think my overall fueling is now OK and only corrections I see in Learn are equally plus and minus based upon envuironmental air temps.

Question. If leak is at the muffler to ext pipe connection why would that matter? deacceleration creates a vac in manifold that will bring in out side air at muffler outlet anyway?

 

Ron,

ECM comes out of DFCO at <1000rpm. Also this area wasn't necessarily just DFCO. When I tune, I will put motor into situations that I wouldn't normally be in when driving around, i.e. crawling in 4th gear at 1200rpm or doing 40mph in 6th to see if I can lug the motor.
When tuning, I'm assuming you've disabled EGR and CCP, correct?
As for your question, leak at the rear Y pipe and muffler joint was close enough to have fresh air go thru cat and affect the NB O2 which is in the header collector. Again this was in low map/low rpm sections of the VE table.

 

Dom: I have DFCO disabled as well as EGR and CPP.

Apparently the Learn can pick up that low RPM/MAP area on deaccelleration then. What I see in my tune is BLMs will move rich and fuel will be pulled on deacceration with low MAP(20) after a lift of pedal deaccelerating from a higher speed of 60 MPH. I was of opinion that was due to my overly rich VE table at 20-30 MAP 1200-1800 rpms. I did check the header flange at exhaust manifold and it appears as a good seal as well.

OK now i understand the area of your leak. My exhaust is dual so I have the mufflers to pipe connection way back in pipe. Guess only muffler I should look at is the one on the NB02 sensor side as far as affecting BLM. I will look at that this weekend

 

Ron,

Are you running a cat? I am, so its acting like an Xpipe in terms of mixing exhaust. Even tho the leak was at the passenger side muffler, it affected my NB O2 on the driver's side collector. Visual inspection may not show up leak. The high vacuum in the exhaust during trailing throttle or decel is what causes exhaust to suck in fresh air. Also, I have DFCO enabled for tuning because I don't want VE Learn at those times.

 

no cat. no emishions at all.

my comment at beginning of my thread was in error. i will use the fudged BPC as I have no other choice as i cannot keep VE uder 100. apparently others have seen this situation as well. No vac leaks I can find. we just confirmed with install of the heated 02 that the header flange to ext pipe is sealed. i also relied on my WB reads of 16.0-16.5/1 and fudged OL CTS/VAC idle table to get the A/F under 15.0/1 at idle. that i am certain was a mistake. My WB may not have been accurrate as I did not recalibrate when I pulled out of barn for start of season. also I fudged the PE table on A/F to get the WB to read 12.5/1. it was reading 10.5/1. that too i believe was a mistake as excessive AE may have been a contributor. so I am using the NON fudged tables for OL and PE. also I had went over the edge on AE and was very rich and affecting the drivability. pulled out 50% of AE fuel and now AE is not bogging car cept just a tad at 2500 rpms with engine under load. i think my last untested AE change will be very close.

WB sensor is dead again. so will replace next week.