Is there a hidden OLSD table causing lean idle for a few minutes on a warm start?
03-30-2011, 07:30 PM
#1
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Is there a hidden OLSD table causing lean idle for a few minutes on a warm start? In HP Tuners? I'm having this issue & found some threads around 2006 dealing with the same thing, but never found any resolutions. My idle AFR is like 17:1 on warm starts & it stays that way for 5-10 minutes. This is only in OLSD & only at idle. As soon as I enable the MAF, the problem either disappears, or is at least much better. Also, as soon as the OLSD AFR comes back in line, I have all VE cells at -1 to -2 & it runs smoother than ever. BUT, the warm start lean idle is an OLSD deal breaker if I cant find a solution.
Anybody have any more info on this?
Also, it's not heat soak, as I have relocated the IAT to my front bumper & it reads outside temp all the time. It was 50 degrees outside today & I still had the lean warm start when running OLSD.
OLFA table doesn't matter either. I can fudge it of course, but as soon as the AFR comes back in line, then I'd be running rich.
Basically, whatever my commanded AFR is, the car idles 2-3 full points leaner & then it all comes back in line after driving around 5-10 minutes. I'm not only getting this data from my AEM wideband, but the car runs much better & doesn't have that lean exhaust stink once the AFR comes back in line. Any ideas?
Anybody have any more info on this?
Also, it's not heat soak, as I have relocated the IAT to my front bumper & it reads outside temp all the time. It was 50 degrees outside today & I still had the lean warm start when running OLSD.
OLFA table doesn't matter either. I can fudge it of course, but as soon as the AFR comes back in line, then I'd be running rich.
Basically, whatever my commanded AFR is, the car idles 2-3 full points leaner & then it all comes back in line after driving around 5-10 minutes. I'm not only getting this data from my AEM wideband, but the car runs much better & doesn't have that lean exhaust stink once the AFR comes back in line. Any ideas?
Last edited by osuhog; 03-31-2011 at 01:19 PM.
03-31-2011, 10:27 AM
#2
Welcome to OLSD, enjoy your stay and try not to go crazy because it happens to everybody. You can use afterstart enrichment to help because it eventually goes away after a few minutes. Seems to be worse with 99-00 operating systems compared to 01-02. Of course the easy thing is to go back to closed loop since you don't have anything exotic for your combo that would necessitate OL.
03-31-2011, 10:44 AM
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Okay, so I guess it's still a normal issue that OLSD people are dealing with. Thanks for the info.
Yeah, my mods aren't wild by any means, but I'm kind of a perfectionist & I just can't get the 02's to perform perfectly in CL. I get just a very slight little bit of surging back & forth at light throttle as the 02's are switching lean-rich-lean-rich, etc. It's not bad by any means, but I don't like it. She runs perfectly smooth in OL with the AFR staying constant & not bouncing back & forth like it does in CL. My LT's & no cats also cause the 02's some small issues at idle. Again, not bad by any means, but I can't bring myself to deal with it when OL is so smooth.
I'll just continue to run OL with MAF enabled, but I have an inquisitive nature & I'd still like to know what's causing this lean OLSD idle if anybody knows.
Thanks again!
Yeah, my mods aren't wild by any means, but I'm kind of a perfectionist & I just can't get the 02's to perform perfectly in CL. I get just a very slight little bit of surging back & forth at light throttle as the 02's are switching lean-rich-lean-rich, etc. It's not bad by any means, but I don't like it. She runs perfectly smooth in OL with the AFR staying constant & not bouncing back & forth like it does in CL. My LT's & no cats also cause the 02's some small issues at idle. Again, not bad by any means, but I can't bring myself to deal with it when OL is so smooth.
I'll just continue to run OL with MAF enabled, but I have an inquisitive nature & I'd still like to know what's causing this lean OLSD idle if anybody knows.
Thanks again!
Last edited by osuhog; 03-31-2011 at 01:22 PM.
03-31-2011, 10:05 PM
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there should be a table somewhere in fueling that shows ect vs startup enrichment.
basically its a multiplier that will mutiply your stoich to richen as its cold and lean it out to your commanded stoich as ect get warmer.
should be commanding 1.00 at 170 ish and above.
just make small increments and check your start up a/f.
basically its a multiplier that will mutiply your stoich to richen as its cold and lean it out to your commanded stoich as ect get warmer.
should be commanding 1.00 at 170 ish and above.
just make small increments and check your start up a/f.
03-31-2011, 10:14 PM
#5
I managed to get mine under control by moving the IAT sensor (which you've already done) and messing with the IAT vs. ECT bias since I have an '02, but that was more of a hack that ended up working rather than the real solution. I gave up trying to figure it out, so I kept it that way and have been fine ever since.
Re-enbling the MAF fixes the problem since it can actually measure the airflow, whereas SD is relying on tables with a set of fixed values that are bound to not cover all possible operating conditions.
Re-enbling the MAF fixes the problem since it can actually measure the airflow, whereas SD is relying on tables with a set of fixed values that are bound to not cover all possible operating conditions.
03-31-2011, 11:08 PM
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What about your cranking VE table, is it good? I don't see how it could keep the thing that lean for that long though. Unless somehow your delay is set really high.
04-01-2011, 08:21 AM
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there should be a table somewhere in fueling that shows ect vs startup enrichment.
basically its a multiplier that will mutiply your stoich to richen as its cold and lean it out to your commanded stoich as ect get warmer.
should be commanding 1.00 at 170 ish and above.
just make small increments and check your start up a/f.
basically its a multiplier that will mutiply your stoich to richen as its cold and lean it out to your commanded stoich as ect get warmer.
should be commanding 1.00 at 170 ish and above.
just make small increments and check your start up a/f.
Also, the afterstart enrichment stuff is meant to decay within a certain amount of camshaft revolutions. I really don't think it's meant to deal with 5-10 minutes of lean condition. I really think something else is at play here.
I managed to get mine under control by moving the IAT sensor (which you've already done) and messing with the IAT vs. ECT bias since I have an '02, but that was more of a hack that ended up working rather than the real solution. I gave up trying to figure it out, so I kept it that way and have been fine ever since.
Re-enbling the MAF fixes the problem since it can actually measure the airflow, whereas SD is relying on tables with a set of fixed values that are bound to not cover all possible operating conditions.
Re-enbling the MAF fixes the problem since it can actually measure the airflow, whereas SD is relying on tables with a set of fixed values that are bound to not cover all possible operating conditions.
Yeah, like I mentioned above, this is definitely something that takes way longer to work itself out than this table could fix unfortunately. All of the cranking tables/afterstart enrichment on my car are still bone stock. I've played with the tables a little just to see how they work, but I always end up right back at the stock settings, which is where they are now.
Thanks again guys, sounds like this is just a hidden/unknown issue with no real solutions at this point.
Last edited by osuhog; 04-01-2011 at 08:31 AM.
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04-01-2011, 09:09 AM
#8
I think you're probably understanding exactly what I'm talking about. As a matter of fact, I believe you were involved in some of the threads I found about this from a few years ago. Unfortunately the bias deal doesn't work with the '99 OS in my car. If I had some extra HPT credits, I would try a newer OS, but unfortunately I don't.
A big part of the problem is that HPT/EFI Live/others only display a portion of what is available in the actual PCM. New stuff is added all the time, but I'm guessing some stuff isn't as easy to figure out since they are reverse engineering the PCM, so they don't include it in the list of stuff accessible to the end user. That said, I'm not even sure there is anything in there that could possibly fix the issue since GM originally designed SD as a failsafe mode in case of MAF failure - it was never intended to be used full time like some of us try to do, and the lack of robustness is apparent with issues such as these.
04-01-2011, 10:19 AM
#9
The bias table of the newer 01-02 OS helps but it's not a magic bullet that stops this behavior. Also it's not necessarily that there are tables still hidden that can fix it, it's that when you are in open loop speed density you are running in a backup fail safe mode of the OS that was never meant to be run full time and I would bet they didn't spend a ton of development time on it. The later computers and operating systems have improved in this area with more computing power, etc. Either way it's irritating at most and only lasts for a few minutes after startup on warm starts and doesn't affect WOT, etc.
04-01-2011, 11:06 AM
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Post your tune let's take a look.
Also do you have the correct injector data?
Did you return all of the enrichment tables back to stock after you tuned ve and maf?
(can't remember the names off the top my head)
@212 degrees if your adding enrichment that's a problem. Should be at 1.00
Normal ect should be under 200 f
Obviously if your add enrichment there you will command that multiplied by stoich.
How is your drivability after those warm starts?
Would you trust your life with that wideband?
Not really fond of where you have put your iat sensor.
If I wanted to trick that sensor I would of messed around with the voltage
reference vs removing it from the intake tract.
I wonder what kind of effect that's been having on determining airmass.
I have had the lean start up issue but enrichment was all I needed.
Warm start lean issue I have had also but never at 17:1
Probably as lean as 15:1
I attributed that too the sensor being too cold to read accurately and lagging from the oxygen that might have been sitting in the collector after the vehicle had shutdown.
My drivability never indicated that it was lean, drove fine.
Also do you have the correct injector data?
Did you return all of the enrichment tables back to stock after you tuned ve and maf?
(can't remember the names off the top my head)
@212 degrees if your adding enrichment that's a problem. Should be at 1.00
Normal ect should be under 200 f
Obviously if your add enrichment there you will command that multiplied by stoich.
How is your drivability after those warm starts?
Would you trust your life with that wideband?
Not really fond of where you have put your iat sensor.
If I wanted to trick that sensor I would of messed around with the voltage
reference vs removing it from the intake tract.
I wonder what kind of effect that's been having on determining airmass.
I have had the lean start up issue but enrichment was all I needed.
Warm start lean issue I have had also but never at 17:1
Probably as lean as 15:1
I attributed that too the sensor being too cold to read accurately and lagging from the oxygen that might have been sitting in the collector after the vehicle had shutdown.
My drivability never indicated that it was lean, drove fine.
04-01-2011, 11:47 AM
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If you see AFR commanded and AFR in the pipe diverge,
but come together in "thermal time" that's most likely
temperature effects on air mass, which SD is hostage
to. No matter where you put the IAT it's going to be
wrong for some region of operation. Relocating it makes
it wrong for low airflows, which is good for performance.
If you're closed loop the trims can take it out (can't help
you at WOT anyhow, so favor a WOT-correct IAT). But
you are open loop. Charge bias toward ECT is probably
the answer, but determining the right weight and taper
is a lot of work.
but come together in "thermal time" that's most likely
temperature effects on air mass, which SD is hostage
to. No matter where you put the IAT it's going to be
wrong for some region of operation. Relocating it makes
it wrong for low airflows, which is good for performance.
If you're closed loop the trims can take it out (can't help
you at WOT anyhow, so favor a WOT-correct IAT). But
you are open loop. Charge bias toward ECT is probably
the answer, but determining the right weight and taper
is a lot of work.
04-01-2011, 11:56 AM
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Post your tune let's take a look.
Also do you have the correct injector data?
Did you return all of the enrichment tables back to stock after you tuned ve and maf?
(can't remember the names off the top my head)
@212 degrees if your adding enrichment that's a problem. Should be at 1.00
Normal ect should be under 200 f
Obviously if your add enrichment there you will command that multiplied by stoich.
How is your drivability after those warm starts?
Would you trust your life with that wideband?
Not really fond of where you have put your iat sensor.
If I wanted to trick that sensor I would of messed around with the voltage
reference vs removing it from the intake tract.
I wonder what kind of effect that's been having on determining airmass.
I have had the lean start up issue but enrichment was all I needed.
Warm start lean issue I have had also but never at 17:1
Probably as lean as 15:1
I attributed that too the sensor being too cold to read accurately and lagging from the oxygen that might have been sitting in the collector after the vehicle had shutdown.
My drivability never indicated that it was lean, drove fine.
Also do you have the correct injector data?
Did you return all of the enrichment tables back to stock after you tuned ve and maf?
(can't remember the names off the top my head)
@212 degrees if your adding enrichment that's a problem. Should be at 1.00
Normal ect should be under 200 f
Obviously if your add enrichment there you will command that multiplied by stoich.
How is your drivability after those warm starts?
Would you trust your life with that wideband?
Not really fond of where you have put your iat sensor.
If I wanted to trick that sensor I would of messed around with the voltage
reference vs removing it from the intake tract.
I wonder what kind of effect that's been having on determining airmass.
I have had the lean start up issue but enrichment was all I needed.
Warm start lean issue I have had also but never at 17:1
Probably as lean as 15:1
I attributed that too the sensor being too cold to read accurately and lagging from the oxygen that might have been sitting in the collector after the vehicle had shutdown.
My drivability never indicated that it was lean, drove fine.
SVO 30# Injector data straight from Greg banish Calibrated Success DVD
Enrichment tables are all stock
I am commanding 1.00 at 212 degrees already, but richer than that at colder temps.
Driveability right when I start it up with this lean AFR is okay, but not great. It wants to nearly die if I back out from a parking space & blip the throttle quickly. Driveability is near perfect after 5 minutes when the AFR comes back in line.
I am certain my WB is reading correctly. Like I mentioned above, not only is my WB telling me it's running lean, but the lean exhaust smell is really bad, & again, off idle driveability is not great. I can tell immediately when the AFR comes back in line, just by the way it runs at idle.
I know the IAT reloaction isn't perfect, but I would sure think it reads a lot closer to actual intake temps now than it did before. It would be 70 degrees outside & the IAT would be reading 120 degrees on a hot start scan. It would also creep up in stop & go traffic & it would always take a while to come back down to reality. Again, I feel it is much more accurate now, but I'm certainly not an expert.
I'll get my tune posted later.
Thanks again!
04-01-2011, 07:58 PM
#13
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Looks like you do not have control of closed loop delay. Either way that sounds like a long time before closed loop is enabled, should be less than a minute at normal operating temps.
04-01-2011, 08:31 PM
#14
It has nothing to do with injector data, closed loop delay (it's in OL permanently), charge bias, where the IAT is located, or any other reason that people have listed here. The only way to fix it is to fudge the after start enrichment tables as that's just the way these old operating systems are with open loop speed density on warm starts. I've been down this path YEARS ago, trust me...
04-01-2011, 09:19 PM
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It has nothing to do with injector data, closed loop delay (it's in OL permanently), charge bias, where the IAT is located, or any other reason that people have listed here. The only way to fix it is to fudge the after start enrichment tables as that's just the way these old operating systems are with open loop speed density on warm starts. I've been down this path YEARS ago, trust me...
05-20-2011, 04:24 PM
#18
My car does the exact same thing, and it's an 04 GTO in OLSD. Hot start, idle AFR is 17-18. I sorta get around it by enabling OL STFT. So after idling lean for about 15 seconds, the oxygen sensors come online and get the idle AFR in check via STFTs. This is about the best way I've found around it. Like you though, I don't understand it at all.
06-02-2011, 08:45 PM
#19
I haven't tried it yet, but maybe hitting the test button on my alky control kit would stop the temporary lean condition by bringing the heat soaked IAT sensor back down to reality. Our IAT sensors are notorious for being slow to respond to decreases in temperature. When I get a chance I'll give it a try.
