turbo Silverado lean spikes/stumble

[BLK02WS6]

Working on a friends turbo Silverado with an E38 PCM. I don't have a ton of experience with them, mostly LS1 PCMs... I am thinking that it has a mechanical issue causing the stumble/miss and unburnt fuel is showing up as spikes on the wideband. It is plenty rich right before it happens and the spikes are sporadic and very large - not typical lean tune characteristics. Any help ruling out a tune issue would be appreciated! Tune and log attached.
Thanks!
Bret

[BLK02WS6]

Looks like the problem may have been the spark plugs - the guy he bought it from had the coldest LS race plugs you can buy in it... blowin the candles out! New plugs and we will give it another go.

[Mean Green Z28]

Woo!

Sent from my SAMSUNG-SM-G900A using Tapatalk

[joecar]

Bret, good job on diagnosing the plugs :cheers:

[BLK02WS6]

Bret, good job on diagnosing the plugs :cheers:

Thanks Joe! Hope to get a chance to catch up with you soon! Been far too long my friend!

[joecar]

Thanks Joe! Hope to get a chance to catch up with you soon! Been far too long my friend!Yeah, too long... it'll be nice to chat on the phone :cheers:

[BLK02WS6]

Unfortunately, it still has the issue... I'm going to try disabling the MAF and seeing if it does it. I saw a post on here where someone else had one that kept going lean with VE and MAF together, but wouldn't do it with each alone. His problem turned out to be some of VE calculation tables (forget which ones and I'm at work and can't look) and I tried those same changes, but it isn't helping this one...

[BLK02WS6]

I finally found a stock tune for this OS and started over - may have solved the issue. Still way too rich, but the lean spikes appear to be gone. Fingers crossed...

[Mean Green Z28]

Git 'er done!

Sent from my SAMSUNG-SM-G900A using Tapatalk

[BLK02WS6]

Git 'er done!

Sent from my SAMSUNG-SM-G900A using Tapatalk

LOL- waiting on you!

[BLK02WS6]

This thing has me stumped. Still hitting the same wall at around 3k RPM. Running VE only right now and have it close enough that it shouldn't be doing this. Tune and log attached...

[joecar]

If you're correcting VE (VVE) did you first do this:
- disable MAF (make a MAF DTC trigger immediately)...?
- disable CL, LTFT, STFT...?

[joecar]

Which VVE table are you editing...?

[BLK02WS6]

If you're correcting VE (VVE) did you first do this:
- disable MAF (make a MAF DTC trigger immediately)...?
- disable CL, LTFT, STFT...?

the MAF is unplugged (signal wire)
LTFT are disabled - I am only correcting the boost area trying to get through this trouble spot to make sure it is not mechanical before tuning the whole thing. Just didn't want the LTFTs staying in during PE and effecting fueling

[BLK02WS6]

Which VVE table are you editing...?

B8105 IMTV open 3Bar table

[BLK02WS6]

This thing is really frustrating me! During a pull, it bucks, and IBPW, airflow, and MAF frequency all get spikes. Also the wideband shows large spikes as well. This is in OL with the MAF online. I am going to unhook the signal wire and see what it does with the MAF offine.

I have found other posts with people having similar issues, and none of their remedies have helped this one. I will attach a log and the tune that it came from. Any ideas?

[joecar]

( BTW: 28 pid channels is making the sample rate slow down... try reducing to 24 pid channels, and in Edit->Properties->Logging select Stream Fast. )

( BTW: Log ETCTP instead of TP )

It looks like the ECM is closing the throttle due to exceeding one of the Electronic Throttle sanity tables (in Engine Diagnostics)... it's a matter of figuring out which one and increasing the upper threshold.... but, I see those are already maxed out... it seems the 512 g/s threshold (which is max) might be being exceeded.

Yes, try without MAF.

[BLK02WS6]

Thanks Joe! I thought I got all of the ETC tables, but I'll check again. So, if we are exceeding 512 g/s, that means we have to scale the tune, right?

Tuan - change the logs like he says above - I didn't notice you added some more. Always keep it to 24 channels. Change to ETCTP.

[joecar]

( look at bottom of PIDs tab and/or Data tab to see Pids Channel count... some pids take 2 or more channels )

[joecar]

Yes, you may have to scale VE/MAF/IFR (if you're using MAF).

[BLK02WS6]

Thanks Joe - I was afraid of that... I don't know if he can pass emissions without the MAF.

[joecar]

Disregard the comment "(if you're using MAF)"...

the 512 g/s limit is in any g/s value inside the PCM, we can see it in GM.DYNCYLAIR and GM.DYNCYLAIR_DMA...

if you hit it (via MAF or DYNAIR) you have to scale.

[BLK02WS6]

E38 doesn't have those pids. Those are in g/cyl anyway - don't I need g/s?

[BLK02WS6]

We made a few hits with no MAF, and it definitely doesn't do the same thing... Scaled the same tune and we will hook the MAF back up.

[joecar]

Disregard the comment "(if you're using MAF)"...

the 512 g/s limit is in any g/s value inside the PCM, we can see it in GM.DYNCYLAIR and GM.DYNCYLAIR_DMA...

if you hit it (via MAF or DYNAIR) you have to scale.Ok, I was thinking LS1B (512 g/s limit on MAF and DYNAIR), sorry I switch between LS1B and E38 alot... :doh2:


The E38 does not have this 512 g/s limit on MAF and DYNAIR, but 512 g/s is the maximum value on the throttle sanity tables.

[BLK02WS6]

I wish it was an LS1B... COS5 and good to go! I hate E38! It is definitely hitting something when on the MAF. I'm gonna keep on with this scaled tune and get the VVE worked in and then try the MAF again and see if it hits this wall. The small amount of driving he did last night on the VE with the scaled tune, it looks much better - rich, but much smoother... time will tell. If it would ever stop raining around here so he can drive it more!

[joecar]

When you scale, you also have to look at any table that references airmass (g) on its axis...

you now have to scale the axis, i.e. you have to shift the table contents down.

[BLK02WS6]

Yep, I think I got them all - went through it table by table. I didn't do any trans controller tables though... it seems to shift fine from what he tells me. I read that you may have to do any that reference torque, like the line pressure tables.

[Mean Green Z28]

This is all so foreign to me ... and I'm a foreigner!

Sent from my SAMSUNG-SM-G900A using Tapatalk

[BLK02WS6]

LOL - your just a transplant, not a foreigner :grin:

[joecar]

lol, I'm officially an alien.

[BLK02WS6]

Joe - what would make my laptop keep going to "not responding" while trying to log? It freezes up and I have to restart it. He brought the truck over and I tried to use my laptop to log - never had this problem before... any ideas?

[joecar]

What laptop is it...?

What V7 software build version...?

Is this with FlashScan V2...?

[BLK02WS6]

Toshiba Satelite/1.40GHz/4GB RAM/Windows 10

V7.5.7 (build 299)

Yes, FlashScan V2

[BLK02WS6]

So, with a scaled tune, we got a good pull on it with no MAF, and the spikes aren't there. It was a bit rich, but pulled great even through a shift.

We hooked up the MAF, and the spikes came back - missing and stumbling like before we scaled the tune. What gives? Can we not run the MAF with this much boost?

[joecar]

I think it has to do with C0803, C0804, they have a maximum range of upto 512 g/s... but you scaled, so I don't know...

[BLK02WS6]

I would think if it was to do with those, it would do it in SD, but it doesn't. I'm searching through other posts, but I'm not finding anything so far. I'm stumped. We may just have to run SD and he can plug in the signal wire when he has to go to emissions (and stay out of the boost)... I'll keep trying to figure it out, but this is getting extremely frustrating...

[BLK02WS6]

One other thing I forgot to mention - I kept knocking down the VE table in huge amounts trying to lean it out to commanded, so I got to thinking... the PWM fuel pump maintains pressure much like a regulated setup, but the IFR table is sloped. I changed it to a flat table and the top end of the VE came in much closer. It seems to be working. If only I could figure out this MAF issue... Here is the latest tune and log with no MAF.

[joecar]

One other thing I forgot to mention - I kept knocking down the VE table in huge amounts trying to lean it out to commanded, so I got to thinking... the PWM fuel pump maintains pressure much like a regulated setup, but the IFR table is sloped. I changed it to a flat table and the top end of the VE came in much closer. It seems to be working. If only I could figure out this MAF issue... Here is the latest tune and log with no MAF.Ok, so is that how the PWM fuel pump behaves, it increases rail pressure as MAP increases... if so then a flat IFR makes sense.

[Mean Green Z28]

Ok, so is that how the PWM fuel pump behaves, it increases rail pressure as MAP increases... if so then a flat IFR makes sense.
Yeah the tables have low/normal/high(PE) kpa settings and it's been good at keeping up with the set pressures so far! Still stock pump but injectors don't seem to be maxing out yet and if anything, the wideband readings show rich!

Sent from my SAMSUNG-SM-G900A using Tapatalk

[BLK02WS6]

Finally got this thing straightened out and running pretty good up to 15# of boost. The workings of this damn E38 have me baffled! Had a MAF only tune that was perfect. Got the VVE tune perfect. Put them together, and off by 20% rich... makes no sense to me at all. In the end, I had to work the MAF further to mesh it with the VVE. Then we put it in CL with STFTs only. STFTs are very low and everything looks great. Don't really know how I got rid of the crazy lean spikes we had - they just didn't come back once we got each tune straight separately and put them together... LS1Bs are so much easier and can be fine tuned so much better with the ability to command other than PE... But, it turned out pretty good in the end. One day, after the meth kit, we need to put it on the dyno and see what it'll make.

[joecar]

Good job :cheers:

I too am currently baffled by some E38's.

[BLK02WS6]

Thanks Joe! I appreciate all of your help with this thing!