Why do I still have a lean idle in closed loop?
Why do I still have a lean idle in closed loop? All of this has been done within the last 24 hours via HP Tuners...
VE tuned with all cells no more than +-2.
MAF calibrated with all cells no more than +-2.
RAF tuned with the Russ K cfg file in D & in P.
All fuel trims were reset before tuning & they were all 0 before my initial post-tune start-up.
So, shouldn’t my AFR be pretty much spot on when I go to closed loop? I logged my closed loop idle a few minutes ago & I’m idling at 15 or greater afr.
Any ideas, or do I need to run the car for a while for the trims to settle in? I didn't think I would need to with VE, MAF, & RAF tuned.
I did notcie that the bank 2 ltft is bouncing around & logging negative #'s but none of the other fuel trims are. Do I possibly have a bad 02 sensor?
Thanks.
VE tuned with all cells no more than +-2.
MAF calibrated with all cells no more than +-2.
RAF tuned with the Russ K cfg file in D & in P.
All fuel trims were reset before tuning & they were all 0 before my initial post-tune start-up.
So, shouldn’t my AFR be pretty much spot on when I go to closed loop? I logged my closed loop idle a few minutes ago & I’m idling at 15 or greater afr.
Any ideas, or do I need to run the car for a while for the trims to settle in? I didn't think I would need to with VE, MAF, & RAF tuned.
I did notcie that the bank 2 ltft is bouncing around & logging negative #'s but none of the other fuel trims are. Do I possibly have a bad 02 sensor?
Thanks.
Long tubes at idle are making it hard to keep an O2 sensor
lit.
Try a little experiment. Reset the trims. Then high-idle it
with the pedal, like 3000 RPM or so, for a minute. Then
let it drop to idle while you watch the O2 switching
waveforms. If it starts off with a reasonable switching
density and symmetry, and over a minute or two becomes
irregular and starts to spend most of its time on the floor,
and trims start to creep, this (insufficient exhaust heat)
is your pony.
lit.
Try a little experiment. Reset the trims. Then high-idle it
with the pedal, like 3000 RPM or so, for a minute. Then
let it drop to idle while you watch the O2 switching
waveforms. If it starts off with a reasonable switching
density and symmetry, and over a minute or two becomes
irregular and starts to spend most of its time on the floor,
and trims start to creep, this (insufficient exhaust heat)
is your pony.
Based on your WB, you HPT thinks it's a 5.5% error in fueling, but your NB and PCM only think it's a 1.6% error on one side. I wouldn't sweat it. Too many things come into play with a cammed car @ idle. Overlap, long tubes, O2 and WB location. Different WBs have different levels of accuracy, and at the end of the day, it doesn't really matter what they read or think at part throttle, the fuel trims are gonna do their thing. Keep them happy, worry about your A/F at WOT.
I would make sure that your O2 switch points are all at 450mv. That can also be a problem with doing STFT tuning. Sometimes light loads have you at 350mv which will make you slightly leaner at idle and light loads.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Thanks for the comments guys.
No e10, only 100% gasoline.
I did find out that my WB gauge is reading about .2 too high, so it's going in for warranty service.
I suspect the long tubes or possibly a small leak at the band clamp on the header collector might be giving me some problems at idle keeping it from being perfect also. But like was mentioned above, the fuel trims take care of that, so it's all good.
WOT AFR is great & even accross the board, although with my WB reading .2 lean, it's actually .2 richer than I'm commanding as set up with my WB. I'm okay with that until I get the WB gauge recalibrated though. If I tuned it too lean, that would be a different story, obviously.
Thanks again for the help.
No e10, only 100% gasoline.
I did find out that my WB gauge is reading about .2 too high, so it's going in for warranty service.
I suspect the long tubes or possibly a small leak at the band clamp on the header collector might be giving me some problems at idle keeping it from being perfect also. But like was mentioned above, the fuel trims take care of that, so it's all good.
WOT AFR is great & even accross the board, although with my WB reading .2 lean, it's actually .2 richer than I'm commanding as set up with my WB. I'm okay with that until I get the WB gauge recalibrated though. If I tuned it too lean, that would be a different story, obviously.
Thanks again for the help.
Trending Topics
The Target AFR is set to 14.63 and the PCM is trying to get to that using the Fuel Trims.
The way I look at it if the Wide-Band is properly installed and known to be giving the correct reading then the tune is off. That is why I use a Wide-Band. To check the PCM.
Know I did up a paper some place and if I recall 14.68 = 15.23 if you have E10% on a Wide-Band.
If you change the Target AFR to 14.1 and you have E10% the Wide-Band read Lambda of 1.0. The ignorant Guage will say that the AFR is 14.7, because it is programmed that way.
The way I look at it if the Wide-Band is properly installed and known to be giving the correct reading then the tune is off. That is why I use a Wide-Band. To check the PCM.
Know I did up a paper some place and if I recall 14.68 = 15.23 if you have E10% on a Wide-Band.
If you change the Target AFR to 14.1 and you have E10% the Wide-Band read Lambda of 1.0. The ignorant Guage will say that the AFR is 14.7, because it is programmed that way.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Wow, it's not like this everywhere? 2xLS1 is indeed correct. OK state law requires e10 pumps to be labeled as such. Most every gas station around here that doesn't sell e10 advertises "NO ETHANOL" on their marquee. I don't even pull in to a station unless they have a sign that says "NO ETHANOL".
As far as my issue, I'm working on making sure the v-band clamp is absolutely sealed at the header collector. Between that & getting my wideband gauge fixed to read correctly, I think I'll be spot on.
2xLS1 is indeed correct. OK state law requires e10 pumps to be labeled as such. Most every gas station around here that doesn't sell e10 advertises "NO ETHANOL" on their marquee. I don't even pull in to a station unless they have a sign that says "NO ETHANOL". As far as my issue, I'm working on making sure the v-band clamp is absolutely sealed at the header collector. Between that & getting my wideband gauge fixed to read correctly, I think I'll be spot on.
A possible leak around the WB 02 bung was suggested to me over on the HPT forum. I never found an actual leak, but I used some hi-temp rtv aroud the bung & I also removed the vband clamp from the header collector & smeared some rtv on & re-installed.
Much better now! My WB gauge is much more stable now & it doesnt bounce around nearly as much. I obviously had a very small leak somewhere around that bung.
I think the only issue I have now is because of the long tubes as jimmyblue suggested (thanks!). It's still reading 3-4% lean after idling for a while. If I give it some throttle for a block or 2, it seems like it's warming up the 02's & then it reading perfectly at idle again. That is until it idles for another minute or 2, then it goes back to reading lean again.
Tell me this. Obviously my 02's will be adding fuel in closed loop as it reads a little lean at idle (when it's cold outside anyway). I know my VE & MAF are tuned spot on at idle after making sure the sensor was completely warm as I tuned. Is there any way I can run open loop at idle & then CL everywhere else with HP Tuners? I'm afraid my ltft's are going to add fuel at idle keeping me rich all the time down there, at least in the winter when it's cold outside.
Any other ideas or suggestions?
Thanks again!
Much better now! My WB gauge is much more stable now & it doesnt bounce around nearly as much. I obviously had a very small leak somewhere around that bung.
I think the only issue I have now is because of the long tubes as jimmyblue suggested (thanks!). It's still reading 3-4% lean after idling for a while. If I give it some throttle for a block or 2, it seems like it's warming up the 02's & then it reading perfectly at idle again. That is until it idles for another minute or 2, then it goes back to reading lean again.
Tell me this. Obviously my 02's will be adding fuel in closed loop as it reads a little lean at idle (when it's cold outside anyway). I know my VE & MAF are tuned spot on at idle after making sure the sensor was completely warm as I tuned. Is there any way I can run open loop at idle & then CL everywhere else with HP Tuners? I'm afraid my ltft's are going to add fuel at idle keeping me rich all the time down there, at least in the winter when it's cold outside.
Any other ideas or suggestions?
Thanks again!
Last edited by osuhog; Dec 16, 2010 at 08:56 PM.
