going lean strange glitch at 5200 rpm for a split second

[davez28]

2010 Silverado 4x4 6.2l with tsp vvt 1.2 cam. this is very strange and i would really appreciate any help. after installing my cam during tuning maf only wot it would intermittently go super lean at wot. once it did it it would stay lean on future pulls for a while then clean up and come back. so i tuned in sd only to get my fueling correct in the vve tables. while i was tuning the wot in sd i had the same glitch happen a few times. in sd mode it only happens for a split second around 5200 rpm at wot. dynamic airflow and cylinder air mass show 0 in the scanner but the maf and mad are reading normal. the bank 2 injectors drop out and spark pegs over 50 degrees. you can feel the truck jerk when it happens

log file (5200 rpm glitch) in in sd only mode look at time stamp 13:41.88 at about 5200 rpm
log file (maf only wot) in maf only look around time stamp 6:05.66 went lean winding out 3rd gear

I don't know if the ecm is going bad or what..checked over all my grounds and i think it has to be the ecm or the software

[GHuggins]

I think - and this is just a guess - that your converter slipping is possibly kicking in a torque limit on the trans or a torque limit in general is kicking in??? It acts just like a torque limit - cutting fuel like it is or even just like DFCO except it's not cutting throttle... Has to be a limiter of some sort... I would also disable desoot, but that won't fix your issue... Is it present in all gears or just higher gears?

[davez28]

When I was running MAF only it would start doing it and it would do it in all the gears. But we were thinking it was seeing such a big difference between my untuned ve table that it made it just resort to it. When I had it in SD mode only it would only do it at 5200 RPMs is all I can say I'll have to go back and look at the other logs to see but it probably was the same gear. The strangest thing about it to me is the fact that the MAF and the map AR reading just fine but yet the dynamic airflow goes to zero as well as a cylinder air mass. And why would it just drop the injectors on the bank 2? The torque converter is a new edition. But it's just the Circle D 3000-3200 and it's not a real sloppy stall

[davez28]

Looked at the other logs. Happened in second and third gear around the same RPM. Only did it twice while I was tuning the SD. And really the only way to isolate is when it's in sd only.

[davez28]

I thought about it possibly being a torque limit of some sort too but I would expect the timing to drop. I think spark ramp out is about all the torque management I have enabled in my tune

[GHuggins]

Do you have your factory tune to compare to? It's dropping injectors on both banks even though pw's don't show it - pay attention to your bank 1 and 2 O2's - they both drop out...

[davez28]

Do you have your factory tune to compare to? It's dropping injectors on both banks even though pw's don't show it - pay attention to your bank 1 and 2 O2's - they both drop out...

here is the stock file..thanks for looking

[davez28]

The other time it did it I wasn't logging my bank to injectors so I can't compare on the other one. But bank one was still in. Also notice my fuel pressure spikes like someone just suddenly turned off the spicket

[GHuggins]

Tell you what - log only these parameters - commanded EQ, all of the tps and accelerator pedal channels, delivered engine torque, any torque management types and rpm and only those... It really looks like it's going into DFCO (negative delivered torque, fuel cut and high timing), now what that's because of - that's the question...

[davez28]

I could try that. Might be a couple days till I can do any wot runs. We're in the middle of a snowstorm now

[Chris@HPTuners]

Try logging Air Calc Mode and MAF Sensor State in the scanner. In SD you might need to apply the Speed Density Air Mode patch if its getting stuck in one mode. Make sure you're not triggering any codes like P0101, 121 etc. due to MAF table mods these tests are all still enabled in your tune.

[davez28]

Try logging Air Calc Mode and MAF Sensor State in the scanner. In SD you might need to apply the Speed Density Air Mode patch if its getting stuck in one mode. Make sure you're not triggering any codes like P0101, 121 etc. due to MAF table mods these tests are all still enabled in your tune.

It didn't set any codes. Do you think the speed density air mode patch might correct my problem?

[davez28]

Try logging Air Calc Mode and MAF Sensor State in the scanner. In SD you might need to apply the Speed Density Air Mode patch if its getting stuck in one mode. Make sure you're not triggering any codes like P0101, 121 etc. due to MAF table mods these tests are all still enabled in your tune.

What does the speed density air mode patch do? It's weird because when I noticed the problem I was in mass air flow only and it was acting like it was switching over and sticking in sd. That was when I first noticed I had the problem. And my vve tables were grossly lean because they hadn't been tuned yet.

[davez28]

Another thing if I log the air calc mode and MAF sensor state parameters can I run it in MAF only or Blended? Just wondering if that might shed some light on what was going on when I was in MAF only mode and it went Goofy

[mowton]

When we were in "MAF only" mode the symptom was a very lean (down about 100 g/sec) Dynamic Air Flow which underfueled the real MAF airflow values during the balalnce of the pull. When We went to Speed Density, the symptom was a split second zeroing of Dynamic Airflow (and associated DCA) and max timing (50 degrees) based on a 0 g/cyl airmass but recovered instantantly.

I have seen, even in "MAF only" that the Dynamic Airflow will change right at that magical 4000 rpm point and I have associated that with bad VE values. Once the VE is tuned properly in Speed Density, the transition is smooth. This leads me to believe that no mater what mode we are in, the PCM has some underlying VE validation/filtering of the MAF values even beyound the High RPM Disable setting of 4000 rpm.

Just so all know, I have opened a support ticket on this as well on behalf of Dave.....

Ed M

[GHuggins]

Those channels will let you know whether or not it's actually in SD or not... Will verify if the issue is still present in MAF or SD - your MAF curve does have a dip right where the problem is, but shouldn't cause this... You can add those to the channels I specified and be just fine - just try to keep the channel quantity as low as possible and even change the channel rates for the more important channels to as fast as possible... Just trying to do some quick more precise data acquisitions of certain things right now is all

If it's in SD - you should be setting MAF codes - MAF state will tell you if it's actually failed - I honestly didn't check the dtc section to see if you've even got the MAF failed...

[GHuggins]

When we were in "MAF only" mode the symptom was a very lean (down about 100 g/sec) Dynamic Air Flow which underfueled the real MAF airflow values during the balalnce of the pull. When We went to Speed Density, the symptom was a split second zeroing of Dynamic Airflow (and associated DCA) and max timing (50 degrees) based on a 0 g/cyl airmass but recovered instantantly.

I have seen, even in "MAF only" that the Dynamic Airflow will change right at that magical 4000 rpm point and I have associated that with bad VE values. Once the VE is tuned properly in Speed Density, the transition is smooth. This leads me to believe that no mater what mode we are in, the PCM has some underlying VE validation/filtering of the MAF values even beyound the High RPM Disable setting of 4000 rpm.

Just so all know, I have opened a support ticket on this as well on behalf of Dave.....

Ed M

10SS has confirmed again and again that there is something else at play above 4000rpm's even on transients that we can't figure out - wonder if what your referring to has something to do with that?

[GHuggins]

Just checked - Chris was right - the MAF isn't even failed according to the current tune settings and MAF setup...

[mowton]

10SS has confirmed again and again that there is something else at play above 4000rpm's even on transients that we can't figure out - wonder if what your referring to has something to do with that?

Yes Greg...but our issue here didn't manifest itself until about 5200 rpm but my felling was that must have been the point at which the validation failed and this "intervention" came into play. That is when we tuned the VE in SPedd density and found it to to way off (lean). Now the MAF and VE are pretty spot on, I'll go back and look at the MF hole you mentioned though....

Ed M

[mowton]

Just checked - Chris was right - the MAF isn't even failed according to the current tune settings and MAF setup...

We completed the tune (MAf and VE) and the tune has been put back into blended....

The 5200 rpm lean log was taken while we were in Speed Density...and yes the MAF was failed. The MAF only log was done when High RPM disable was 400/390...

Ed M