trouble with commanded AFR

[erics_02_z06]

I'm sick of my car smelling super rich at idle and stalling sometimes, so today I changed the following on my tune:

Set the PE enrich table to activate at 0 % throttle for 0-1200 rpms with a PE commanded AFR of 15.9.

This is the only thing I changed on the tune. I loaded it up, took the car for a test drive and noticed the following:

The commanded AFR was never above 14.7 at any time. The car died far more times than it ever had....

Any thoughts? I've attached my tune and the log. The cam is a 228/228 so nothing too big. I'm guessing its defaulting to another table that is richer? But even then...I have my OLFA table in the idle ranges set higher than 14.7. I'm guessing there is another factor involved...I just don't know what

[bene]

Why are you messing with PE for your idle issues?

[Higgs Boson]

What kind of car do you have? PE Idle trick only works on some.....

[erics_02_z06]

2002 corvette z06. I'm messing with the PE because I don't know how to command a higher AFR for idle cells. Is there another way to change the Closed Loop AFR for idle? I figured I would just throw it in open loop and command a higher AFR to lean it out a little. The idle is the only part of the tune I never quite got perfect.

[erics_02_z06]

one last idea...what about the proportional idle thresholds. Apparently, it the TPS if below 5% on my tune, it activates the "idle proportional closed loop fueling tables" Which I'm sure are richer than my open loop OLFA or PE tables...so maybe it defaults to this closed loop mode instead of my open loop commanded AFR's? I don't want to go messing with to many things I don't fully understand so input is greatly valued. Thanks

[Bill@HPTuners]

It has nothing to do with power enrich or OLFA, etc. it has everything to do with the EPA. There is no way to command a leaner mixture than 14.7:1 without enabling lean cruise which we are not going to enable for the sake of staying in business.

[erics_02_z06]

Well.....I disabled the "idle proportional closed loop fueling tables"....and the car started targeting a 15.5 during idle which it didn't before. I am not 100 % certain that this was the problem though...I think my usb cable was also jacked up because I noticed when the car wasn't moving it was still reading vehicle speed. HOWEVER....The stumble was mostly gone when coming to a stop so I'm thinking that disabling the closed loop fueling tables helped.


So....Here is my new question.....is targeting a 15.5 too lean with my size cam? I don't have all the specs in front of me, but I know its a 228/228/.580 with a 112 lsa I believe. I ask this because I did have a check engine light start flashing half way through my drive then disappear.

[Tongboy]

It has nothing to do with power enrich or OLFA, etc. it has everything to do with the EPA. There is no way to command a leaner mixture than 14.7:1 without enabling lean cruise which we are not going to enable for the sake of staying in business.

ugh, that just doesn't seem right to not allow a owner of something to make changes to it.

how can leaning out a vehicle be a bad thing? aside from the obvious issue of going too lean and potentially grenading your motor while you aren't busy blowing your motor up you are contributing less emissions to the environment, who would be against that?

[MikeGyver]

It has to be at 14.7:1 for the cats to work their magic.

[erics_02_z06]

I took the car for another drive, changed nothing, and it was dying like crazy...not sure how that works since it drove amazing before.

Honestly, that's the story of this car. Some days absolutely no issue....then other days, it wants to die when I come to a stop or hunts like crazy for the target idle.

Maybe a failing TPS? I noticed that during the stages where my car kept hunting for the idle ( I took my foot off of the gas completely to log the data) that my tps kept increasing from 7% to 10% then back to 7% or so, this was followed by an increase and drop in RPM, which created a MAP swing and a swing in commanded AFR per the OLFA table if that makes sense. Maybe this is the cause of my erratic idle?

God I'm sick of this....

[Higgs Boson]

could be a lot of things, timing, VE, etc.... retune your VE and set your timing to a fixed value on and all around your idle cells, then make sure it is nice and smooth.

[PLP]

how can leaning out a vehicle be a bad thing? aside from the obvious issue of going too lean and potentially grenading your motor while you aren't busy blowing your motor up you are contributing less emissions to the environment, who would be against that?

Cat needs the fuel to be switching around stoich to work and going leaner creates more nox emissions , although it drops co2

[erics_02_z06]

what should the timing be set to as a starting point. Can u point me in the direction of a good idle tuning guide?

[JDS]

What other modifications have been done? Since your TPS is less than 5%, I am guessing it is still the original LS6 manifold and throttle?

I'm not on my personal cpu to open your tune and log. Everyone will probably have their own variation of approaches, but I would:
- put the fuel tables back to commanding 1.000
- put your PE enable back to it's previous settings
- crank it up and let it idle until the idle stabilizes, and take note of how much air is being added for idle trimming (assuming it is low, and because the russK idle config won't be accurate if the idle is hunting)
- manually adjust your timing while the idle is steady to find where it is most stable and has the most vacuum. (lowest manifold pressure)
- Shut down and add the idle trimmed air value across the board on your base idle airflow table, and set your timing tables for idle and high octane to the settled timing value. Make sure adjacent cells are the same as well so that only the overspeed/underspeed tables are changing the commanded timing.
- crank back up when cold and run the idle config to get the correct values for your base airflow table (I have added about 5% over typically to ensure I won't get dipping).
- If it is still hunting, try adjusting your overspeed/underspeed timing tables to be more or less agressive (both ways have worked independently for me).

I have a FAST 90/90 setup with a 231/239 113 cam and 243 heads on my '99, and it idles great at 850rpm all day with no dipping or dying. Correct airflow and timing are key, and you shouldn't need to jack with fueling tricks if these are correct. With any decent overlap, and closed loop fueling commanding 1.0 lambda, it is always going to run a bit richer than commanded at idle because of the extra air getting through that the oxygen sensors "adjust" for like a pseudo lean condition.

Keep in mind if trying to command too far outside of 1.0, that the narrow band oxygen sensors are not intended to be used much beyond stoich and will not be accurate.

Good luck

[erics_02_z06]

What other modifications have been done? Since your TPS is less than 5%, I am guessing it is still the original LS6 manifold and throttle?

I'm not on my personal cpu to open your tune and log. Everyone will probably have their own variation of approaches, but I would:
- put the fuel tables back to commanding 1.000
- put your PE enable back to it's previous settings
- crank it up and let it idle until the idle stabilizes, and take note of how much air is being added for idle trimming (assuming it is low, and because the russK idle config won't be accurate if the idle is hunting)
- manually adjust your timing while the idle is steady to find where it is most stable and has the most vacuum. (lowest manifold pressure)
- Shut down and add the idle trimmed air value across the board on your base idle airflow table, and set your timing tables for idle and high octane to the settled timing value. Make sure adjacent cells are the same as well so that only the overspeed/underspeed tables are changing the commanded timing.
- crank back up when cold and run the idle config to get the correct values for your base airflow table (I have added about 5% over typically to ensure I won't get dipping).
- If it is still hunting, try adjusting your overspeed/underspeed timing tables to be more or less agressive (both ways have worked independently for me).

I have a FAST 90/90 setup with a 231/239 113 cam and 243 heads on my '99, and it idles great at 850rpm all day with no dipping or dying. Correct airflow and timing are key, and you shouldn't need to jack with fueling tricks if these are correct. With any decent overlap, and closed loop fueling commanding 1.0 lambda, it is always going to run a bit richer than commanded at idle because of the extra air getting through that the oxygen sensors "adjust" for like a pseudo lean condition.

Keep in mind if trying to command too far outside of 1.0, that the narrow band oxygen sensors are not intended to be used much beyond stoich and will not be accurate.

Good luck

k, I'll give this a try. honestly though....I get sick of the running rich at idle because I smell like gas so bad after I drive

[Russ K]

k, I'll give this a try. honestly though....I get sick of the running rich at idle because I smell like gas so bad after I drive

Installing cats is the only way to eliminate the gas smell. Been there before.

Russ Kemp

[erics_02_z06]

Installing cats is the only way to eliminate the gas smell. Been there before.

Russ Kemp

thanks man, I was wondering about that. I guess I'll just smooth this thing out and not worry about leaning the idle out

[erics_02_z06]

not to beat a dead horse...but this is really starting to get under my skin. I've done tons of searching, and read a million posts, but no solution.

here is my new gripe:

Started car, car was in open loop (warming up)
Started driving, car was in closed loop (cruising)
Came to stop , car was in open loop using the PE commanded value at idle
Started driving again, car remained in open loop the remainder of the drive, and fueled off of the OLFA

why the hell won't it go back to CL?? I tried making the whole OLFA table leaner than 14.68 hoping that would throw it into CL, not a chance....

[Russ K]

Your most likely setting an O2 low voltage code, thus switching to open loop.

I'm in closed loop at idle with a G5X3 114 (234/242) camshaft, and no issues with gas smell as I have high flow cats.

Russ Kemp

[erics_02_z06]

russ-
I disabled the low voltage codes...now the car is either in OL-Accel/Decel, or CL. Any ideas? When it is OL-Accel/Decel, it commands 14.681. It stays in that mode even while idle. I've attached a log.